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UNIVERSITY  OF 
CALIFORNIA 


EARTH 

SCIENCES 

LIBRARY 


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THE 


GEOLOGICAL   STORY 

BRIEFLY   TOLD. 

Introtwrtion  to 


FOR 


THE  GENERAL  READER  AND  FOR  BEGINNERS 
IN  THE  SCIENCE. 


BY 

JAMES    D.   DANA,   LL.D., 
// 

AUTHOR  OF   "A  MANUAL  OF  GEOLOGY,"    "  TEXT- BOOK   OF  GEOLOGY,"    "CORALS   AND 
CORAL  ISLANDS,"    WORKS  ON  MINERALOGY,  ETC. 


WITH  NUMEROUS  ILLUSTRATIONS. 


NEW  YORK  AND  CHICAGO  : 
IVISON,   BLAKEMAN,   TAYLOR,  AND   COMPANY. 

1875. 


<n 
I 

&  .    te  C& 


COPYRIGHT,  1875. 
BY  IVISON,  BLAKEMAN,  TAYLOR,  &  CO. 


UNIVERSITY  PRESS:  WELCH,  BIGELOW,  &  Co. 
CAMBRIDGE. 


SCIENCES 

LIBRARY 


PREFATOET    SUGGESTIONS. 


EOLOGY  is  eminently  an  out-door  science ;  for  strata,  rivers, 
\A  oceans,  mountains,  valleys,  volcanoes,  cannot  be  taken  into  a 
recitation-room.  Sketches  and  sections  serve  a  good  purpose  in  illus- 
trating the  objects  of  which  the  science  treats,  but  they  do  not  set 
aside  the  necessity  of  seeing  the  objects  themselves.  The  reader  who 
has  any  interest  in  the  subject  should  therefore  go,  for  aid  in  his 
study,  to  the  quarries,  bluffs,  or  ledges  of  rocks  in  his  vicinity,  and  all 
places  that  illustrate  geological  operations.  At  each  locality  accessi- 
ble to  him  he  should  observe  the  kinds  of  rocks  that  there  occur ; 
whether  they  consist  of  layers  or  not ;  and  their  positions,  whether  the 
layers  are  horizontal,  —  the  positon  they  had  when  made  ;  or  whether 
inclined,  —  a  slope  in  the  beds  being  evidence  of  a  subterranean 
movement  like  that  which  takes  place  in  mountain-making. 

Geology  teaches  that  much  the  larger  part  of  the  rocks  that  con- 
sist of  layers  were  made  through  the  action  of  water ;  and  if  such 
rocks  are  accessible,  it  is  well,  after  learning  the  lessons  of  the  book, 
to  look  among  them  for  evidence  of  this  mode  of  origin,  either  in 
the  structure  of  the  layers,  in  the  nature  of  the  material,  in  markings 
within  the  beds,  or  in  the  presence  of  relics  of  aquatic  life,  such  as 


iv  PREFATORY   SUGGESTIONS. 


shells,  bones,  etc.  If  some  of  the  layers  in  a  bluff  consist  of  sand- 
stone, others  are  pebbly,  others  clayey,  and  one  or  more  are  of 
limestone,  the  kinds  of  changes  in  the  waters  that  took  place  to  pro- 
duce so  varied  results  should  be  made  a  point  for  investigation. 

If  an  excavation  for  a  cellar  is  opened  near  an  accustomed 
walk,  it  is  best  to  look  at  the  sections  of  the  earth  or  sands  thus 
made ;  for  these  sands  are  very  often  in  layers,  and,  in  that  case,  they 
bear  evidence  that  there  even  the  loose  material  of  the  surface  had 
been  arranged  by  water,  either  that  of  the  ocean  or  that  of  a  river 
or  lake. 

When  the  layers  contain  fossils,  a  collection  should  be  made  for 
study ;  for  they  show  what  living  species  populated  the  waters  or 
land  when  the  rocks  were  forming  ;  and  in  the  height  of  a  single 
bluff  there  may  be  records  thus  made  of  several  successive  popula- 
tions different  from  one  another. 

If  a  beach  or  a  cliff  along  the  ocean  is  accessible,  the  action  of 
the  waves  in  their  successive  plunges  may  be  watched  to  great  ad- 
vantage ;  for  they  are  thus  grinding  up  the  stones  and  sands  of  the 
beach,  and  eroding  and  undermining  the  cliff.  While  viewing  such 
work  on  a  seashore,  it  will  be  a  good  time  to  consider  that  this  bat- 
tering goes  on  almost  incessantly  through  the  year,  and  year  after  year, 
and  has  so  gone  on  along  coasts  and  about  reefs  for  indefinite  ages. 
The  cliff  and  the  rocky  ledges  in  the  surf  at  its  base  should  be  closely 
examined,  that  the  amount  and  kind  of  wear  may  be  appreciated ;  and 
the  action  of  the  water  over  the  beach  should  be  studied  in  order 
to  understand  why,  after  so  much  grinding,  coarse  sands  and  often 
pebbles  are  still  left. 


PREFATORY  SUGGESTIONS. 


If  there  are  sand-flats  exposed  off  the  shores  at  low  tide,  there 
is  a  chance  to  discover  by  what  currents  or  movements  of  the  water 
they  were  formed,  and  whence  came  the  sands  that  compose  them, 
which  should  be  taken  advantage  of;  for  they  are  identical  in  kind 
and  mode  of  origin,  although  not  in  extent,  with  the  sand-flats  of 
ancient  time  out  of  which  sandstones  have  been  made ;  the  only  pos- 
sible difference  being  that  in  the  earlier  ages  the  waters  were  every- 
where salt,  and  rivers  gave  little  aid.  And  if  the  sandy  surface  is 
left  rippled  as  the  tide  goes  out,  note  this,  for  ancient  sandstones 
often  contain  such  ripple-marks  over  their  layers ;  or  if  the  muddy 
portions  are  marked  with  the  tracks  of  Mollusks,  note  this  also,  for 
in  many  rocks  just  such  tracks  occur. 

If  coral  reefs  or  shell  rocks  are  forming  along  the  shores,  —  as  in 
the  West  Indies,  —  these  formations  should  receive  special  study ; 
for  many  of  the  old  limestones  of  the  world  were  made  in  the  same 
way. 

If  a  heavy  rain  has  gullied*  a  side-hill  or  proved  disastrous  to 
roads,  here  is  a  fruitful  field  for  study ;  for  the  gullies  are  minia- 
ture valleys,  and  they  illustrate  how  most  great  valleys  were  ex- 
cavated, —  the  latter  being  as  truly  the  work  of  running  water  as 
the  former.  The  same  gullied  slope  may  exemplify  also  the  for- 
mation of  precipices  and  waterfalls,  of  crested  ridges,  table-topped 
summits,  and  groups  or  ranges  of  mountain-peaks. 

These  are  some  of  the  points  of  easy  observation.  Many  others 
will  occur  to  the  reader  after  a  perusal  of  the  following  pages. 

A  few  labelled  specimens  of  minerals  and  rocks  are  absolutely  in- 
dispensable for  even  a  partial  understanding  of  the  subject,  and  the 


vi  PREFATORY   SUGGESTIONS. 

student  should  buy  or  beg  them,  if  not  able  to  do  the  better  thing 
of  collecting  them. 

Of  MINERALS:  1,  crystallized  quartz;  2,  two  or  three  quartz  pebbles 
of  different  colors ;  3,  the  variety  of  quartz  called  horustone  or  flint ;  4, 
common  feldspar ;  5,  mica ;  6,  black  hornblende ;  7,  a  black  or  greenish- 
black  crystal  of  augite,  and  better  if  in  a  volcanic  rock ;  8,  garnet ;  9, 
tourmaline ;  10,  calcite  (carbonate  of  lime),  a  cleavable  specimen  ;  11,  dolo- 
mite, or  magnesian  carbonate  of  lime ;  12,  gypsum,  or  sulphate  of  lime ;  13, 
pyrite  (sulphid  of  iron) ;  14,  magnetite,  or  magnetic  iron  ore ;  15,  hematite, 
or  specular  iron  ore  ;  16,  limonite,  the  common  iron  ore  often  called  "brown 
hematite "  ;  17,  siderite,  or  spathic  iron  ore ;  18,  chalcopyrite,  or  yellow 
copper  ore ;  19,  galenite,  or  lead  ore  (sulphide  of  lead) ;  20,  graphite. 

Of  ROCKS  :  1,  2,  3,  common  compact  limestone  of  three  different  colors, 
one,  at  least,  of  the  specimens  with  a  fossil  hi  it ;  4,  chalk,  a  variety  of 
compact  limestone ;  5,  6,  white  and  clouded  granular  or  crystalline  lime- 
stone, of  which  the  ordinary  architectural  marble  is  an  example;  7,  8, 
red  and  gray  sandstone ;  9,  conglomerate,  called  also  pudding-stone ;  10, 
shale,  such  as  the  slaty  rock  of  the  coal-formation,  and  other  shales  of  the 
Silurian  and  Devonian ;  11,  slate,  or  argillyte,  that  is,  common  roofing- 
slate,  or  writing-slate ;  12,  13,  coarse  and  fine-grained  grayish  or  reddish 
granite  (to  be  obtained,  like  marbles  and  sandstones,  in  many  stone-yards) ; 
14,  red  or  gray  syenyte,  of  which  the  Scotch  "  granite  "  and  Quincy  "  gran- 
ite "  are  good  examples ;  15,  gneiss,  a  piece  that  has  the  mica  distinctly 
in  planes,  and  hence  is  banded  on  a  surface  of  transverse  fracture;  16, 
mica  schist;  17,  trap,  an  igneous  rock;  18,  trachyte,  an  igneous  rock; 
19,  lava,  a  cellular  volcanic  rock ;  20,  a  piece  of  diatom  or  infusorial  earth. 

The  above-mentioned  minerals  should  at  least  be  accessible  to  a 
class,  if  not  in  the  hands  of  each  student ;  and  it  would  be  well  if 


PREFATORY   SUGGESTIONS. 


vn 


the  collection  were  larger.  Moreover,  the  instructor,  if  not  a  prac- 
tical geologist,  should  have  by  him  the  writer's  Manual  of  Geology, 
or  some  other  large  work  on  the  science,  in  order  to  be  ready  to 
answer  the  questions  of  inquisitive  learners,  and  add  to  the  exam- 
ples and  explanations. 

The  student  should  possess  a  hammer  and  a  chisel.     The  best 
hammer  has  the  face  square,   flat,   sharp-angled,  and   the   opposite 
end  brought  to  an  edge ;   this  edge  should 
have  the  same  direction  with  the  handle  (as 
in  the  figure),  if  it   is  to  be  used  for  get- 
ting  out   rock-specimens,  but  be  transverse 
to  this,  and  thinner,  if  for  obtaining  fossils. 

The  socket  for  the  handle  should  be  large,  in  order  that  the  handle 
may  stand  hard  work.  The  chisel  should  be  a  stone-chisel,  six 
inches  long.  Rock  -  specimens  should  be  uniform  in  size,  with 
straight  sides ;  say  two  inches  by  three,  or  three  inches  by  four. 
Fossils  had  better  be  separated  from  the  rock  if  it  can  be  done 
safely. 

For  measuring  the  dip,  that  is,  the  slope,  of  layers,  an  instrument 
called  a  clinometer  is  used,  which  can  be  had 
of  the  instrument-makers.  It  is  a  compass 
having  a  pendulum  hung  at  the  centre,  the 
extremity  of  which  swings  over  a  graduated 
arc.  In  the  best  kind  the  compass  is  three 
inches  in  diameter  and  has  a  square  base.  A 
clinometer  apart  from  the  compass  may  be 
easily  extemporized  by  taking  (see  figure)  a  piece  of  board,  abed, 


viii  PREFATORY  SUGGESTIONS. 

cut  to  an  exact  square  (three  or  four  inches  each  side),  hanging  a 
pendulum  on  a  pivot  near  one  angle  («),  describing  on  the  board, 
with  one  leg  of  the  dividers  on  the  pendulum-pivot,  an  arc  of  90° 
(b  to  c),  and  then  dividing  this  arc  into  nine  equal  parts,  each  to 
mark  10°,  and  subdividing  these  parts  into  degrees.  Such  a  cli- 
nometer, well-graduated,  is  sufficiently  accurate  for  good  work. 

Field  work  of  the  kind  above  pointed  out  makes  the  facts  in  the 
science  real.  It  also  teaches  with  emphasis  the  great  lesson  that  ex- 
isting forces  and  operations  are  in  kind  the  same  that  have  formed 
the  rocks,  the  valleys,  and  the  mountains.  It  thus  prepares  the 
mind  to  appreciate  geological  reasoning  and  comprehend  the  march 
of  events  in  the  earth's  history. 

NEW  HAVEN,  CONN.,  February  1,  1875. 


TABLE    OF    CONTENTS. 


PAGE 
GEOLOGY       1 

PART  L  — ROCKS,  OR  WHAT  THE  EARTH   IS   MADE   OF. 

I.  MINERALS 3 

1.  Consisting  of  Silica .    ,        3 

2.  Silicates 5 

3.  Carbon  and  Carbonates 8 

4.  Ores .         .10 

II.  KINDS  OP  ROCKS 13 

III.  STRUCTURE  OF  ROCKS 19 


PART   II.  — CAUSES   IN   GEOLOGY,  AND  THEIR   EFFECTS. 

I.   MAKING  OF  ROCKS 23 

1.  Ways  in  which  Plants  and  Animals  have  contributed  to  Rock- 

making  27 

1.  Making  of  Limestones 27 

2.  Making  of  Siliceous  Rocks  or  Masses     .         .         .         .35 

3.  Making  of  Peat-beds 40 

2.  Quiet  Work  of  Air  and  Moisture 42 

3.  The  Work  of  Winds 44 

4.  The  Work  of  Fresh  Waters 46 

5.  The  Work  of  the  Ocean 50 

6.  The  Work  of  Ice 57 

7.  The  Work  of  Heat  in  Rock-making 63 

1.  Through  Expansion  and  Contraction       .         .         .         .63 

2.  Through  Fusion :  Volcanoes 64 

3.  Solidification,  Metamorphism,  and  Formation  of  Veins     .  70 


TABLE  OE   CONTENTS. 


II.  MAKING  or  VALLEYS     .        .        . 76 

III.  MAKING  OF  HILLS  AND  MOUNTAINS  AND  THE  ATTENDANT  EFFECTS  80 

1.  Mountains  made  by  Igneous  Ejections 80 

2.  Mountains  and  Hills  produced  by  the  Erosion  of  Elevated  Lands  81 

3.  Mountains  made  by  Upturnings   and  Flexures  of  Rocks,  and 

Bendings  of  the  Earth's  Crust 83 


PART  III.  —  HISTORICAL   GEOLOGY. 

SUBJECTS  AND  SUBDIVISIONS 96 

I.   ARCELEAN  TIME         .        .        .     • 106 

1.  Distribution          .      •  .         . 10? 

2.  Rocks      .      :  .      •  ,      •  .        ,         i';      ....  109 

3.  Life     ...-."•.-.....         .         .111 

II.  PALEOZOIC  TIME     •  .  •  •  .'        .        .        .        .        .        .        .  113 

1.  Silurian  Age,  or  Age  of  Invertebrates 113 

1.  Lower  Silurian 115 

2.  Upper  Silurian 129 

3.  Observations  on  the  Silurian  Age     ....  134 

2.  Devonian  Age,  or  Age  of  Fishes 137 

1.  Rocks 137 

2.  Life  .         .         .         .        .         .         .         .         .         .  139 

3.  Mountain -making  .......  148 

3.  Carboniferous  Age,  or  Age  of  Coal  Plants        ....  149 

1.  Rocks.  —  Coal-measures 150 

2.  Life 156 

3.  Changes  during  the  Progress  o£  the  Carboniferous  Age  164 

4.  Mountain-making  at  the  Close  of  Paleozoic  Time     .         .         .167 

Changes  in  Paleozoic  Life  at  the  Close  of  the  Era      .  173 

III.  MESOZOIC  TIME    .        . 174 

Age  of  Reptiles .  174 

1.  Rocks        .........  175 

2.  Life ':•'.-        '  18° 

3.  Mountain-making  in  Mesozoic  Time    ....  193 


TABLE  OF  CONTENTS.  xi 


IV.  CENOZOIC  TIME 194 

1.  The  Tertiary,  or  Age  of  Mammals 194 

1.  Rocks 195 

2.  Life 200 

3.  Mountain-making 206 

4.  Climate 209 

2.  Quaternary  Age,  or  Era  of  Man 209 

1.  Glacial  Period 211 

2.  Champlain  Period 218 

3.  Recent  Period 221 

4.  Life  of  the  Quaternary 224 

5.  Geological  Work  still  going  Forward    .         .         .         .235 

V.   OBSERVATIONS  ON  GEOLOGICAL  HISTORY 237 

1.  Length  of  Geological  Time 237 

2.  Progress  in  Features 240 

3.  The  System  of  Nature  of  the  Earth  had  a  beginning  and  will 

have  an  end 241 

4.  Progress  in  Life 242 


INDEX.  257 


ILLUSTRATIONS. 

THE  original  sources  of  the  larger  part  of  the  illustrations  will  be  found 
stated  in  the  author's  Manual  of  Geology.  Of  the  few  not  in  the  Manual, 
Fig.  11  is  from  a  photograph  taken  by  the  artist  of  Powell's,  Expedition ; 
Figs.  13  to  16,  from  the  author's  "Corals  and  Coral  Islands";  Fig.  33, 
from  H.  J.  Clarke's  "  Mind  in  Nature " ;  and  Fig.  46,  from  an  electro- 
type kindly  furnished  by  the  publishers  of  the  "American  Naturalist," 
Salem. 


GEOLOG-Y. 


THE  word  Geology  is  from  two  Greek  words  signifying  the 
story  of  the  earth.  As  used  in  science,  it  means  an  ac- 
count of  the  rocks  which  lie  beneath  the  surface  and  stand  out 
in  its  ledges  and  mountains,  and  of  the  loose  sands  and  soil 
which  cover  them;  and  also  an  account  of  what  the  rocks 
are  able  to  tell  about  the  world's  early  history.  By  a  careful 
study  of  the  nature  and  positions  of  rocks,  and  the  markings  or 
relics  they  contain,  it  has  been  discovered  how  the  rocks  them- 
selves were  made;  and  also  how  the  mountains  and  the  conti- 
nents, with  all  their  variety  of  surface,  were  gradually  formed. 
And,  further,  it  has  been  ascertained  not  only  that  the  earth  had 
plants  and  animals  long  before  Man  appeared,  but  what  were 
the  kinds  that  existed  in  succession  through  the  long  ages. 
The  subjects,  therefore,  of  which  geology  treats  are :  — 

I.  The  KINDS  OF  ROCKS. 

II.  The  ways  in  which  the  rocks,  valleys,  mountains,  and 
continents  were  made,  —  or  CAUSES   IN  GEOLOGY,  AND  THEIR 
EFFECTS. 


GEOLOGY. 


III.  The  events  during  the  successive  periods  in  the  earth's 
history;  that  is,  what  making  of  rocks  was  going  on  in  each 
period,  what  making  of  mountains'  and  valleys,  and  what  spe- 
cies were  living  in  the  waters  and  over  the  land  in  each,  and 
how  the  world  of  the  past  differs  from  the  world  as  it  now  is,  — 
all  of  which  subjects,  and  others  related,  are  treated  under  the 
general  head  of  HISTORICAL  GEOLOGY. 


PART    I. 

ROCKS,  OR  WHAT  THE  EARTH  IS  MADE  OF. 

BOCKS  consist  of  minerals ;  and  the  ores  and  gems  they  con- 
tain are  minerals.  Any  mineral  that  yields  a  metal  profitably  is 
called  an  ore. 

The  following  are  the  characters  of  some  of  the  kinds  that 
are  of  most  importance  in  geology. 
i 

I.  —  Minerals. 

I .  Consisting  of  Silica. 

Quartz.  —  Quartz  is  the  most  common  of  the  materials  of 
rocks.  It  is  well  fitted  for  this  first  place ;  for  (1)  it  is  one  of 
the  hardest  of  minerals,  the  point  of  a  knife-blade  or  edge 
of  a  file  making  no  impression  on  it;  (2)  it  does  not  melt  in 
the  hottest  fire ;  and  (3)  it  is  not  dissolved  by  water,  or  cor- 
roded by  either  of  the  common  acids.  Its  durability  is  its 
great  quality.  "With  a  piece  of  quartz  it  is  easy  to  write  one's 
name  on  glass.  Another  quality  of  it,  distinguishing  it  from 
many  minerals  it  resembles,  is  that  it  breaks  as  easily  in  one 
direction  as  another. 


4          ROCKS,  OE  WHAT  THE  EARTH  IS  MADE  OF. 

It  is  of  various  colors  and  kinds.  Flint  and  hornstone  are 
dark-colored  massive  quartz.  The  smooth-surfaced  stones  of  a 
pebble-bank,  whether  white,  brown,  yellow,  or  black,  if  uni- 
form (not  speckled)  in  color,  are  almost  all  quartz.  Moun- 
tains thousands  of  feet  high  are  sometimes  made  of  quartz 
rocks.  The  sands  of  a  sea-shore  are  mostly  quartz,  because  the 
grinding  of  particle  against  particle  which  goes  on  under  the 
heavy  dash  or  swift  flow  of  the  waters  wears  out  all  other 
materials,  and  leaves  only  the  hard  quartz  particles  behind. 

Quartz  is  often  found  in  crystals.  The  figure  annexed  shows 
the  form  of  one  of  them.  It  is  a  regular  6-sided  prism  (i  i  i), 

Fig.  i.  with  a  6-sided  pyramid  at  each  end ;  and  it  is  often 
as  transparent  as  glass.  Frequently  the  crystals  are 
attached  by  one  end  in  great  numbers  to  a  surface 
of  rock,  so  that  this  surface  is  brilliant  with  little 

Quartz.  pyramids  of  quartz  set  crowdedly  over  it,  or  with 
pryamids  raised  on  prisms.  The  inclination  of  the  face  of  the 
prism  to  the  adjoining  face  of  the  pyramid  is  always  the  same 
(141°  47'),  wherever  the  quartz  crystal  may  come  from.  These 
glassy  crystals  are  wholly  natural  productions,  having  their 
forms  perfect  and  lustre  brilliant  when  first  taken  from  the 
rocks. 

While  some  quartz  crystals  are  clear  and  colorless,  others 
have  a  purple  color,  and  these  are  the  amethyst  of  jewelry. 
Others  have  a  light-yellow  color,  looking  like  topaz,  and  are 
called  false  topaz ;  and  others  a  clear  smoky-brown  color,  and 
these  are  the  cairngorm  stone  of  Scotland. 


MINERALS  CONSTITUTING  ROCKS. 


Still  other  kinds  of  quartz  are  the  agates,  in  which  the  color 
is  arranged  in  thin  bands  or  layers  of  different  shades  of  color, 
as  white,  smoky-brown,  red,  etc. 

The  material  of  quartz  is  called  in  chemistry  silica,  from  the 
Latin  word  silex,  meaning  flint. 

Quartz,  while  so  enduring,  when  pulverized  and  heated  fuses 
easily  with  soda,  potash,  lime,  magnesia,  or  oxyd  of  iron,  and 
forms  a  kind  of  glass;  and  ordinary  glass  is  made  by  melting 
together  quartz  sand  and  soda.  Again,  hot  waters  containing 
soda  or  potash  in  solution  will  dissolve  silica,  and  on  cooling 
deposit  it  again.  The  waters  of  hot  springs  usually  contain 
silica,  which  they  have  taken,  along  with  soda  or  potash,  from 
some  rock  with  which  they  have  been  in  contact.  Through 
deposits  from  such  solutions  (1)  agates  have  been  made;  (2) 
fissures  in  rocks  have  been  filled  with  quartz,  and  the  fractures 
thus  mended;  and  (3)  the  sands  of  sand-beds  and  gravel  of 
gravel-beds  have  often  been  cemented  into  the  hardest  of  rocks. 

Opal  is  also  silica,  but  it  differs  from  quartz  in  being  softer, 
of  less  specific  gravity,  and  never  crystallized ;  and  in  %e 
precious  opal  it  has  a  beautiful  play  of  colors  arising  from 
internal  reflections.  The  silica  of  diatoms  and  of  some  de- 
posits made  by  geysers  is  in  the  state  of  opal. 

2.  Silicates. 

Silica,  while  existing  in  rocks  abundantly  as  quartz,  also 
makes,  on  an  average,  a  third  of  all  their  other  minerals, 


C  ROCKS,  OR  WHAT  THE  EARTH  IS  MADE  OR 

limestones  excepted;  that  is,  it  exists  combined  with  other 
substances,  making  various  common  minerals.  These  minerals 
containing  silica  are  called  silicates. 

L  Feldspar,  —  The  most  universal  of  these  silicates  are  the 
kinds  called  feldspar.  Besides  silica,  a  feldspar  contains  the 
elements  of  alumina,  and  of  potash,  soda,  or  lime.  Corun- 
dum is  nothing  but  alumina ;  and  the  beautiful  gem  sap- 
phire is  only  a  clear  blue  variety  of  it;  and  the  hard  emery 
used  for  grinding  and  polishing,  and  often  in  little  emery- 
bags  for  sharpening  needles,  is  the  same.  It  is  the  hardest 
of  all  stones  excepting  the  diamond,  and  hence  it  is  a  good 
companion  for  quartz  or  silica  in  rock-making.  The  two, 
silica  and  alumina,  in  combination  together  make  minerals 
that  are  harder  and  no  less  infusible  than  quartz;  but  when 
combined  also  with  potash,  soda,  lime,  or  iron,  the  minerals 
it  forms  melt  more  or  less  easily. 

Feldspar  has  usually  a  white  or  flesh-red  color,  and  some- 
times might  be  mistaken  for  quartz.  But  (1)  it  is  not  quite 
so  hard  as  quartz,  though  too  hard  to  be  scratched  with  a 
knife;  and,  besides,  (2)  it  melts  when  highly  heated;  (3)  it 
breaks  in  one  direction  with  a  bright  even  surface,  brilliant  in 
the  sunshine,  and  also  in  another  direction  at  right  angles 
or  nearly  so  to  the  former,  but  less  easily,  —  a  kind  of 
fracture  called,  in  mineralogy,  cleavage.  While  quartz  has 
no  cleavage,  feldspar  has  cleavage  in  two  directions  trans- 
verse to  one  another. 


MINERALS  CONSTITUTING  ROCKS. 


Common  feldspar  (called  orthoclase  in  mineralogy)  is  a  pot- 
ash-feldspar, it  containing  the  elements  of  potash  along  with 
those  of  alumina  and  silica ;  another  is  a  soda-feldspar 
(albite)  ;  others  are  soda-and-lime  feldspars,  and  one  of  these, 
called  labradorite,  is  a  constituent  of  many  igneous  rocks ; 
and  another  is  a  lime-feldspar. 

2.  Mica.  —  Mica   (often  wrongly  called  isinglass)  splits  very 
easily  into  leaves  thinner  than  the  thinnest  paper,  which  are 
tough   and  elastic,   and  frequently   transparent.      It   does   not 
melt  easily,  but  fuses  on  the  thin  edges  with  high  heat.     It 
is  the  transparent  material  commonly  used  in  the   doors   of 
stoves.     Some  mica  is  white,  or  gray;  it  is  oftener  brownish, 
and   very    frequently    black.     Like    feldspar,   it    contains    the 
elements  of  silica  and  alumina;   the  most  common   light-col- 
ored kind  has,  besides  these  constituents,   potash ;    the  black 
kind  contains  magnesia  and  iron. 

3.  Hornblende.  —  Black    hornblende,    when     occurring    in 
rocks,  often  looks  much  like  mica,  showing  lustrous  cleavage 
surfaces;   but  it  is  a  brittle  mineral,  and  hence  cannot,  like 
mica,  be   split   into   thin,  flexible   leaves    or   scales   with  the 
point  of  a  knife.     It  makes  very  tough  rocks,  and  hence  the 
first  part  of  the  name,  horn;  the  rocks  are  heavy  and  some- 
times look  like   an   ore  of  iron,  and  hence   the   second   part, 
blende,   a   German  word   meaning   blind   or   deceitful.      It  is 
a  silicate,   that   is,   it   contains   silica,   but   with  it  there  are 
iron,  magnesia,  and  lime.     There  are  other  kinds  of  hornblende, 
but  they  need  not  be  mentioned  here. 


8  ROCKS,  Oil  WHAT  THE  EARTH  IS  MADE  OF. 


4.  Augite.  —  Augite  is  black  or  dark-green  pyroxene,  hav- 
ing the  same  composition  as  hornblende,  and  differing  only  in 
the  shape  of  its  crystals.  It  is  named  from  a  Greek  word 
signifying  lustre,  because  its  crystals  are  often  bright,  though 
not  more  so  than  those  of  hornblende. 

Two  of  the  crystals  of  hornblende  are  represented  in  Figs. 
2,  3,  and  one  of  those  of  augite  in  Fig.  4.  The  angle  of 

Figs.  2-5. 


Minerals. 
Figs.  2,  3,  Hornblende ;  4,  Augite  ;  5,  Garnet  in  mica  schist 

the  prism  of  augite  (or  that  between  /  and  /  in  Fig.  4) 
is  about  87°;  while  the  angle  of  the  prism  of  hornblende  (be- 
tween /  and  I  in  Fig.  2)  is  124^° ;  it  is  owing  to  this  differ- 
ence mainly  that  hornblende  and  augite  have  distinct  names. 

5.  Garnet  —  Usually  in  dark-red  crystals,  but  often  also 
black,  and  occurring  imbedded  in  mica  schist  and  other  rocks ; 
as  represented  in  Fig.  5,  contains  silica,  alumina,  iron,  and 
lime.  When  transparent  it  is  used  as  a  gem. 

3.   Carbon  and  Carbonates. 

Carbon  is  familiarly  known,  though  in  a  state  not  quite 
pure,  as  common  charcoal.  The  diamond  is  crystallized  car- 


MINERALS  CONSTITUTING  ROCKS.  9 

bon,  and  can  be  burnt  like  charcoal,  though  not  without  in- 
tense heat.  Graphite  (or  black  lead,  as  it  is  often  badly 
named,  since  it  contains  no  lead)  is  also  carbon;  it  is  the 
material  of  lead-pencils. 

Carbon  combined  with  oxygen  in  certain  proportions  forms 
carbonic  acid,  an  ingredient  of  the  atmosphere,  it  constituting 
4  parts  by  volume  of  10,000  parts  of  air;  it  is  the  gas  that 
escapes  from  effervescent  waters  like  soda-water.  Its  com- 
pounds are  called  carbonates. 

L  Calcite.  —  Calcite  occurs  in  crystals  that  break  easily  in 
three  directions,  affording  forms  with  rhombic  faces,  like  Fig. 
6;  the  angles  between  the  faces  are  105°  5' 

If  IgS.   O  •  O« 

and  74°  55'.  A  very  common  form  is  called 
dog-tooth  spar ;  the  shape  is  shown  in  Fig. 
7.  Another  kind  is  a  6-sided  prism  with 
a  low  pyramid  at  either  end  (Fig.  8).  Cal- 
cite is  easily  scratched  with  the  point  of  a 
knife.  In  a  rock  form,  it  is  limestone. 
When  calcite  or  limestone  is  burnt,  carbonic  acid  escapes  as 
a  gas,  and  lime  (called  quicklime,  the  material  that  slacks 
in  water  and  is  used  for  making  mortar)  is  left.  Calcite  is 
carbonate  of  lime.  When  a  grain  of  calcite  is  put  into  di- 
lute hydrochloric  (muriatic)  acid,  carbonic  acid  gas  is  given 
off  freely,  producing  a  brisk  effervescence,  and  the  calcite  be- 
comes wholly  dissolved  if  it  is  pure.  By  means  of  (1)  its 
effervescence  with  acid,  (2)  its  low  degree  of  hardness,  (3) 
i* 


10   ROCKS,  OR  WHAT  THE  EARTH  IS  MADE  OF. 

its  infusibility  in  the  hottest  fire,  and  its  burning  to  quick- 
lime instead,  calcite  or  limestone  is  easily  distinguished  from 
feldspar  and  other  minerals.  The  cleavages  in  calcite  also 
separate  it  from  feldspar;  for  the  number  of  directions  is 
three,  and  the  angle  between  them  is  about  105°  instead  of 
about  90°. 

2.  Magnesian  Limestone,  or  Dolomite.  —  Limestone  sometimes 
contains  magnesia  in  place  of  part  of  the  lime,  and  it  is  then 
called,  in  mineralogy,  dolomite,  after  Dolomieu,  a  French 
geologist  of  the  last  century.  Dolomite,  or  magnesian  lime- 
stone, does  not  effervesce  freely  unless  the  acid  is  heated,  and 
in  this  respect  it  differs  from  calcite.  In  aspect,  calcite  and 
dolomite  are  closely  alike. 

4.  Ores. 

The  following  are  a  few  of  the  common  ores. 

1  Pyrite.  —  Pyrite  has  nearly  the  color  and  lustre  of  brass. 

It  is  so  hard  that  it  will  strike  fire  with  steel  (whence  its  name, 

from  the  Greek  for  fire),  and  in  this  it  differs  from  a  yellow 

ore   of   copper,   called   chalcopyrite   or   copper   pyrites,   which 

it  much   resembles.     It  is  very  often  in  cubes, 

Fig.  9. 

like  Fig.  9.     It  consists   of  sulphur  and  iron, 


nearly   48   parts   by  weight  in   100  being  iron. 
Both  of   these   elements   have    a   strong  affinity 
for  oxygen;  and  consequently  pyrite  often  changes 
to  vitriol,   or   else   forms   the    oxyd  of  iron  called  limonite. 


MINERALS  CONSTITUTING  ROCKS.  11 

It  is  of  no  use  as  an  ore  of  iron,  because  of  the  difficulty 
of  separating  the  sulphur;  but  it  is  often  employed  for  the 
making  of  vitriol  (sulphate  of  iron).  It  is  the  most  gener- 
ally distributed  of  all  metallic  minerals,  occurring  in  particles 
through  most  rocks,  crystalline  as  well  as  uncrystalline.  Ow- 
ing to  the  tendency  to  alteration  just  mentioned,  it  has  caused 
the  destruction  or  disintegration  of  rocks  over  the  earth's  sur- 
face to  a  greater  extent  than  any  other  agency. 

2.  Magnetite,   or  Magnetic  Iron  Ore,  —  An  iron-black  ore 
of  iron,  having  a  black  powder.     It  is  attractable  by  the  mag- 
net.    It  is  common  in  Northern  New  York,  Orange  County, 
New    York,    Sussex   County,   New   Jersey,   and    many    other 
regions.     It   consists   of   oxygen   and   iron   in   the   proportion 
of   4   atoms   of  the   former  to  3  of  the  latter,  and   contains 
72  parts  of  iron  in  100. 

3.  Hematite,  or  Specular  Iron  Ore.  —  A  steel-gray  ore  of 
iron,  but   often  also  bright  red,  the  powder   being  red.     Bed 
ochre  is  an  earthy  hematite.     It  is  not  attracted  by  a  mag- 
net.     Like  magnetite,   it   occurs  in   great  beds  in  Northern 
New  York,  in  the  Marquette  region,  near  Lake  Superior,  in 
Michigan,  and  many  other  places.     It  consists  of  oxygen  and 
iron  in  the  proportion   of  3  atoms  of  the  former  to  2  of  the 
latter,  and   contains,  when  pure,  70  parts   by  weight  of  iron 
in  100. 

All  rocks   of  a  reddish  or  red  color  owe  the  color  to  this 
oxyd  of  iron. 


12 


ROCKS,  OB  WHAT  THE  EARTH  IS  MADE  OF. 


Hematite  and  magnetite    occur,  with  -all  exceptions,  in 
beds  instead  of  veins.     When  the  beds  are  verbal  or  nearly 

so  they  look  like  veins. 

I  Lonite.-A  brown,  brownish-yellow,  or  black  ore  of 
•mn,  affording   a    Iro^-yello*    powder,    sometimes   eal 
«  «,     Yellow  ochre  is  impure  or  earthy  1—  . 
It  differs  in  composition  from  hematite  only  in  contanung  wa- 
r.   and  if  heated  the  water  is  dnven  off,  and  *  becomes 
red'  or  hematite.     It  contains,  when  pure,  about  60  per  cent 
of  |ron     It  is  a  result  of  the  decomposition  of  other  won  ores, 
nd  fonns  great  beds  in  some  regions,  as  near  Salisbury  ,n 
Connecticut,  and  Richmond  in  Massachusetts.    It  ,  often  found 
in  bogs,  and  is  then  called   log-iron  ore.    Lunomte 
disseminated  through  clays,  giving  them  a  yellowish  or  brown 
ish  color;  and  such  clays  when  heated  turn  red,  because  thy 
1  the  water  which  makes  limonite  to  differ  from  hemat^ 
This  is  the  reason  that   bricks  are   usually   red.     Clay 


*ti 

bonicacid.    When  pure  about  48  parts 

occurs  crystallized,  and  also  in  impure  massrve  nodular  form. 

The  iron  ore  of  many  coal.regions   is   thi,   mass.ve  nodule 

SsK 


grayish  or  browmsh  stones. 


KINDS  OF  ROCKS.  13 


effervesces,  owing  to   the   escape   of  carbonic  acid.     This  ore, 
like  limonite,  is  sometimes  present  sparingly  in  clays. 

6.  Chalcopyrite,   or  Yellow    Copper   Ore.  —  A    brass-colored 
mineral  consisting  of  sulphur,  iron,  and  copper,  about  a  third 
of  which  is  copper.     It  is  scratched  easily  with  a  knife,  and 
affords   a    dark-green    powder,    and    thus    differs   from  pyrite, 
which  it  resembles.      It   occurs  for  the    most  part  in  veins 
with  other  ores. 

7.  Galenite,   or  Lead  Ore.  —  A  lead-gray   ore,  brittle    and 
easily  pulverized,  and   affording  a  lead-gray  powder.     It  often 
cleaves   into   cubic   or   rectangular   forms.     It   is  the  common 
lead   ore.     It   often   contains  a  little   silver,  and  is  sometimes 
worked  as  a  silver   ore.     It   occurs   in   cavities  in  limestones, 
as  in  Northern  Illinois,  Wisconsin,  and  Missouri,  and  in  Der- 
byshire,   England ;     and   is    often   found    also    in   veins   with 
other  ores. 

II.  —  Kinds  of  Rocks. 

THE  following  are  the  characters  of  some  of  the  common 
kinds  of  rocks. 

1.  Limestone ;  Magnesian  Limestone. — These  rocks  are  partly 
described  on  pages  9  and  10.  They  are  of  dull  shades 
of  colors,  from  white  through  gray,  yellow,  red,  and  brown 
to  black,  and  of  all  degrees  of  texture,  from  that  of  flint  to. 
a  coarse  granular  texture.  The  test  by  acids,  by  heat,  and 
by  a  use  of  the  point  of  a  knife  in  trial  of  the  hardness, 


14         ROCKS,  OK  WHAT  THE  EARTH  IS  MADE  OF. 

are  the  means  of  distinguishing  limestones  from  other  rocks. 
Chalk  is  limestone.  Ordinary  marble  is  limestone,  and  some- 
times the  magnesian  kind. 

The  different  kinds  of  limestone  are  called  calcareous  rocks, 
from  the  Latin  calx,  meaning  lime. 

2.  Sandstone.  —  Sandstone  is  a  rock  made   of  sand.      The 
sand   may   be   quartz,   like   the    sand    of  most   sea- shores,   or 
pulverized  granite   or   other   rock;    when  gathered   into   beds 
and  consolidated,  it  makes  sandstone.     Sandstones  are  the  most 
common  of  rocks.     They  have  various  dull  colors,  from  white 
through  gray,  yellow,  and  brown  to  brownish-red  and  red. 

3.  Conglomerate.  —  A  conglomerate   or  pudding-stone  is   a 
consolidated  gravel-bed,  —  gravel  being  sand  mixed  with  peb- 
bles or  small  stones.     The  stones  are  sometimes  large,  even  a 
foot  in   diameter.     They  are   often   of  quartz,    sometimes   of 
other  hard  rocks,  and  occasionally  of  limestone. 

4.  Shale.  —  Shale  is  a   fine  mud  or  clay  consolidated  into 
a   rock    having   a   slaty   fracture,    but   less    evenly    slaty    and 
less   firm   than  true   slate.      The   colors   vary,  like   the   colors 
of  mud   or  clay,  from  gray  and  yellowish  shades  through  red 
and  brown  to  black.     Black  is  a  common  color,  because   the 
plants   and  animals  that   live   and  die  in   the   mud  or  over  it 
contain  carbon,  the  chief  element  of  coal,  and  contribute  por- 
tions  of  carbonaceous    substances   to   the   mud.      Such  black 
shales,  when  burnt,  usually  become  white  or  nearly  so,  because 
the   vegetable    or    animal   material   is   then   burnt   out.      For 
the   same  reason  black  limestones  afford  white  quicklime. 


KINDS  OE  ROCKS.  15 

The  loose  earthy  material  of  the  world,  in  and  out  of  the 
water,  is  mostly  either  sand,  gravel,  mud,  or  clay;  and  thus 
it  has  been  through  all  ages.  Sand  is  finely  pulverized  rock. 
Mud  is  the  same,  for  the  most  part;  but  it  may  contain 
rock  that  is  decomposed  as  well  as  pulverized.  Clay  is  a 
fine  kind  of  mud;  it  is  mainly  either  pulverized  feldspar 
along  with  quartz  in  fine  grains,  or  else  decomposed  feldspar 
with  more  or  less  quartz.  It  comes  from  the  pulverizing  of 
granite,  gneiss,  and  other  rocks  containing  feldspar,  or  from 
their  decomposition.  Clay  often  contains  iron;  and  when 
burnt  to  make  brick  it  then  becomes  red.  Gravel  is  mixed 
sand  and  pebbles. 

The  consolidation  of  sand  makes  sandstones;  of  pebble- 
beds,  conglomerates;  of  fine  mud  or  clay,  shale. 

5.  Argillaceous    Sandstone.  —  When    sands   are   clayey,   the 
beds  make,  when  consolidated,  a  clayey,  that  is,  argillaceous, 
sandstone   (argilla,  in  Latin,  meaning  clay).     Such  sandstones 
usually  break  into  thin  slabs,  in  which  case  they  are  said  to 
be  laminated  sandstones;    and,  if   of  sufficient  hardness,  they 
make   good  flagging-stone  for  sidewalks.      The   common   flag- 
ging-stone  used    in    New   York    and    adjoining   States   is   an 
argillaceous  sandstone. 

6.  Slate.  —  Slate,  or  argillyte,  differs  from   shale  in  break- 
ing much  more  evenly,  and  being  much  firmer.      The  slates 
used  for  roofing  are  examples. 

7.  Granite.  —  Granite   is   one   of   the   crystalline  rocks,   its 


16        ROCKS,  OR  WHAT  THE  EARTH  IS  MADE  OF. 

ingredients  being,  not  worn  grains  like  those  of  a  sandstone 
or  conglomerate,  but  crystalline  grains,  —  all  having  been 
rendered  crystalline  together  by  a  process  in  which  heat  was 
concerned  (p.  26).  It  consists  of  grains  of  three  minerals, 
quartz,  feldspar,  mica,  mixed  promiscuously  together.  The 
quartz  grains  are  usually  grayish  or  smoky  in  color  (com- 
monly of  a  darker  tint  than  the  feldspar),  and  have  no  cleav- 
age. The  grains  of  feldspar  have  cleavage,  and  therefore 
show  smooth,  sparkling  surfaces  when  a  fragment  of  granite 
is  exposed  to  the  sun,  and  their  color  is  usually  white  or 
flesh-red.  The  mica  is  much  softer  than  the  feldspar,  and 
with  a  point  of  a  knife-blade  its  grains  may  be  divided  into 
thin,  flexible  scales;  its  colors  are  white,  brownish,  or  black. 

8.  Gneiss.  —  Gneiss  has   the  same   constituents   as   granite; 
but  these  constituents   are   arranged   more   or  less   in   planes, 
and,  owing  to  the  mica,  the  rock  splits  into  thick  layers,  and 
on  a  cross  fracture  appears  banded.     On  account  of  its  split- 
ting into   layers   gneiss   is   said   to   be   a   schistose   rock    (this 
term  being  derived  from  a  Greek  word  meaning  to  divide,  and 
pronounced   as  if  spelt   shistose}.     This  schistose   structure  is 
the  only  one  distinguishing  it  from  granite.     It  is   somewhat 
like  the  laminated  structure. 

9.  Mica  schist.  —  Mica  schist  has  the  same  constituents   as 
granite   and   gneiss,   but  the  quartz   and   mica  are   much   the 
most  abundant,  and  especially  the  mica;     and  on  account  of 
the   large   proportion   of  mica,   mica   schist   divides   into   thin 


KINDS  OF  ROCKS.  17 


layers.  It  glistens  in  the  sunshine,  owing  to  the  scales  of 
mica.  Sometimes  the  scales  of  mica  are  indistinct,  and  then 
it  is  called  mica  slate. 

The  crystalline  rocks,  granite  and  gneiss,  and  gneiss  and 
mica  schist,  pass  into  one  another  through  indefinite  shadings. 
There  are  granites  that  are  slightly  gneiss-like,  and  all 
grades  to  true  gneiss;  and  there  are  all  grades  from  gneiss 
to  mica  schist,  so  that  it  is  sometimes  difficult  to  say 
whether  a  rock  should  be  called  granite  or  gneiss,  and 
whether  another  should  be  called  gneiss  or  mica  schist. 
Again,  mica  schist  shades  off  through  mica  slate  into  argil- 
lyte,  or  clay  slate,  as  the  crystalline  texture  is  less  and  less 
apparent. 

10.  Syenyte.  —  Some  granite-like  rocks  contain  hornblende 
in  place  of  the  mica,  and  such  kinds  are  called  syenyte.  The 
hornblende  is  grayish-black,  greenish-black,  or  black,  and 
differs  from  black  mica  in  being  brittle,  and  hence  in  not 
affording  thin,  flexible  scales.  This  fact  indicates  the  kind 
of  examination  to  be  made  to  distinguish  syenyte  from 
granite.  The  so-called  granite  of  the  Quincy  quarries,  near 
Boston,  and  the  red  Scotch  granite  imported  for  monuments, 
are  syenyte. 

II  Syenyte  Gneiss ;  Hornblende  Slate.  —  Syenyte  gneiss  differs 
from  ordinary  gneiss  in  containing  hornblende  instead  of 
mica.  Hornblende  schist  or  slate  is  a  black  slaty  rock  con- 
sisting mainly  of  hornblende. 

B 


18    ROCKS,  OR  WHAT  THE  EARTH  IS  MADE  OF. 

12.  Trap;  Volcanic  Eocks,  —  Trap  is  an  igneous  rock:  that 
is,  it  has  cooled  from  fusion,  like  the  lavas  of  a  volcano. 
It  came  to  the  surface  in  a  melted  state,  through  an  opened 
fissure,  from  some  deep-seated  region  of  liquid  rock.  The 
part  filling  a  fissure  is  called  a  dike.  It  has  sometimes 
flowed  from  the  fissure  over  the  adjoining  country.  Trap 
is  a  dark-colored,  heavy  rock,  more  or  less  crystalline  in  tex- 
ture. It  consists  of  a  lime-and-soda  feldspar  (called  labra- 
dorite,  from  Labrador,  where  it  was  first  found)  and  augite, 
along  with  grains  of  magnetite.  It  is  the  rock  of  the  Pali- 
sades along  the  west  side  of  the  Hudson  River  above  New 
York,  of  Mount  Holyoke  near  Northampton,  and  various 
other  hills  and  ridges  in  the  Connecticut  Valley;  of  many 
ridges  in  the  vicinity  of  Lake  Superior,  and  over  the  west- 
ern slope  of  the  Rocky  Mountains;  of  the  Giant's  Causeway 
on  the  north  coast  of  Ireland,  and  Staffa  on  the  western 
coast  of  Sco'tland;  and  is  common  over  the  globe. 

Some  trap  contains  small  nodules  consisting  of  different 
minerals.  These  nodules  fill  cavities  that  were  made,  while  the 
rock  was  still  melted,  by  expanding  vapors.  This  variety  of 
trap  is  called  amygdaloid,  because  the  little  nodules  sometimes 
have  the  shape  of  almonds  (amygdalum,  in  Latin,  meaning 
almond}.  Trap,  especially  if  very  fine  grained,  is  often  called 
basalt.  It  frequently  occurs  in  columnar  forms,  as  at  the 
Giant's  Causeway,  many  places  in  the  Lake  Superior  region, 
and  elsewhere. 


STRUCTURE  OF  ROCKS.  19 

Volcanic  rocks,  called  lavas,  are  those  that  have  been  ejected 
in  a  melted  state  from,  or  about,  an  open  vent  called  (from  the 
Latin  for  bowl)  a  crater.  Eruptions  around  the  crater  make 
the  fire-mountain,  or  volcano. 

The  larger  part  of  lavas,  and  of  all  igneous  rocks,  are  simi- 
lar in  composition  to  trap,  although  often  very  cellular  rocks, 
and  sometimes  resembling  much  the  scoria  of  a  furnace. 

Other  volcanic  and  igneous  rocks  are  mainly  feldspar  in 
composition,  and  as  they  therefore  contain  little  or  no  iron, 
they  are  less  heavy  than  trap.  Their  specific  gravity  is  mostly 
2.5  to  2.8,  while  that  of  the  trap  series  is  2.8  to  3.2.  A  com- 
mon kind,  rough  on  a  surface  of  fracture,  is  called  trachyte; 
and  another,  containing  isolated  crystals  of  feldspar,  is  porphyry. 

Sand-rocks  made  out  of  volcanic  sands  are  called  tufas. 

III.  —  Structure  of  Rocks. 

L  Stratified  Rocks.  —  Most  rocks  consist  of  layers  piled  one 
upon  another;  and  the  series  in  some  regions  is  thousands  of 
feet  in  height.     Figure  10  rep- 
resents a  bluff  on  the  Genesee 
River  at  the  falls  near  Roches- 
ter.   In  this  section  Nos.  1  and 
2  are  sandstone;   No.  3,   green 

i     -I          -»T         ,      , .  --  Section  on  Genesee  Kiver. 

shale;  No.  4,  limestone;  No.  5, 

shale;  No.  6,  limestone;  No.  7,  shale;  No.  8,  limestone  again. 


20   ROCKS,  OR  WHAT  THE  EARTH  IS  MADE  OF. 


Fisr.  11. 


Part  of  the  wall  of  the  Colorado  Canon,  from  a  photograph  by  Powell's  Expedition. 

Another  example  is  here  presented  (Fig.  11)  from  the  Colo- 
rado Canon.  The  height  of  the  pile  of  layers  in  view  is  over 
3,110  feet;  but  the  river  flows  2,755  feet  below,  and  hence 
the  whole  height  of  the  wail  is  5,865  feet.  Still  another 
example  from  the  Colorado  region  is  given  on  page  78. 

It  is  to  be  noted  that  (1)  the  layers  were  made  one  after 
another,  beginning  with  the  lowest;  that  (2)  the  successive 
layers  correspond  to  successive  intervals  of  time  in  geological 
history. 


STRUCTURE  OF   ROCKS.  21 

Eocks  consisting  thus  of  beds  are  called  stratified  rocks, 
from  the  Latin  stratumj  meaning  bed. 

But  layer  and. stratum  in  geology  have  not  the  same  mean- 
ing. In  Fig.  10  the  lower  sandstone  bed,  No.  1,  consists 
of  many  layers;  together  they  make  a  stratum.  No.  3  is 
another  stratum, — one  of  shale;  No.  4,  another, — one  of  lime- 
stone, and  also  made  up  of  many  layers;  and  so  on.  Thus 
there  are  eight  strata  (strata  being  the  plural  of  stratum]  vis- 
ible in  the  bluff;  and  each  consists  of  many  layers.  All  the 
layers  of  one  kind,  lying  together,  make  one  stratum. 

Sandstone,  shale,  conglomerate,  and  limestone  are  the-  most 
common  kinds  of  stratified  rocks.  Gneiss  and  mica  schist  are 
also  of  this  nature,  although  crystalline  in  texture. 

2.  TTnstratified  Rocks.  —  Unstratified  rocks  are  not  made  up 
of  layers.  The  granite  about  the  Yosemite,  in  California,  is  in 
lofty  mountains  and  mountain-domes,  showing  no  distinct  bed- 
ding or  stratification;  and  the  same  is  the  character  of  most 
granite.  The  trap-rocks  of  the  Palisades,  on  the  Hudson,  rise 
boldly  from  the  water  and  have  no  division  into  layers;  but, 
instead,  a  vertical  division  into  imperfect  columns,  —  a  com- 
mon feature  of  such  trap-rocks,  illustrated  on  the  next  page.  It 
is  not,  however,  true  that  all  igneous  rocks  are  ^stratified ;  for 
where  lavas  have  flowed  out  in  successive  streams  over  a  region, 
those  streams  have  made  successive  beds,  and  the  rocks  are 
truly  stratified.  But  the  term  stratified  rocks  is  usually 
applied  only  to  the  kinds  not  of  igneous  origin. 


22 


HOCKS,  OR  WHAT  THE  EAKTH  IS  MADE  OE. 


The  columnar  structure  of  some  trap-rocks  is  well  illustrat- 
ed in  the  following  view  of  a  scene  on  the  shores  of  Illawarra 

Fig.  12. 


Basaltic  columns,  coast  of  Illawarra,  New  South  Wales. 

in  New  South  Wales,  Australia.  While  stratification  has  come 
from  the  successive  formation  of  beds,,  these  columns  are  a 
result  of  the  cooling.  Cooling  causes  contraction,  and  the 
contraction  of  the  solid  rock  as  cooling  went  on  produced 
the  fractures.  These  fractures  are  always  at  right  angles,  or 
nearly  so,  to  the  cooling  surfaces.  Where  the  rock  fills  ver- 
tical fissures,  the  columns  are  horizontal.  Even  sandstones 
have  been  rendered  columnar  where  overlaid  by  beds  of  trap, 
or  when  they  have  been  subjected  otherwise  to  heat. 


PART  II. 

CAUSES  IN  GEOLOGY,  AND  THEIR  EFFECTS. 

UNDER  the  head  of  Causes,  Geology  treats  of  the  ways 
in  which  (1)  rocks,  (2)  valleys,  (3)  mountains  and  continents 
were  made;  or,  in  general,  the  means  through  which  all 
changes  have  been  brought  about. 

I.  —  Making  of  Rocks. 

THE  rocks,  briefly  described  in  the  preceding  pages,  have 
been  made  by  the  following  methods. 

L  Rocks  formed  from  fusion.  —  Igneous  rocks  are  here  in- 
cluded, or  those  that  have  cooled  from  a  melted  state  after 
ejection  from  some  seat  of  fire  within  the  earth.  They  are 
crystalline  in  texture,  each  grain  being  a  separate  crystal; 
yet  the  small  grains  are  so  crowded  together  that  they  have 
nothing  of  the  external  forms  of  crystals,  and  sometimes  they 
are  too  minute  to  be  easily  distinguished.  Igneous  rocks  are 
of  small  extent  and  importance  over  the  globe  compared  with 
those  made  through  the  action  of  water. 

2.  Rocks  made  by  deposition  from  waters  holding  the  mate- 


24  CAUSES  AND  THEIR  EFFECTS. 

rial  of  them  in  solution.  —  Waters  containing  lime  often  de- 
posit it,  and  so  make  a  kind  of  limestone. 

Waters  percolating  through  the  limestone  roofs  of  caverns, 
as  they  evaporate  on  the  roof,  form  long  pendent  cones  or 
cylinders  of  limestone  called  stalactites  (from  the  Greek  for 
to  distil) ;  and  the  same  waters,  dropping  to  the  floor  of  the 
cavern,  there  evaporate  and  produce  a  bed  of  limestone  called 
stalagmite. 

There  are  many  springs,  and  a  few  rivers,  in  the  world, 
whose  waters  are  calcareous.  They  petrify  the  moss,  leaves, 
and  nuts  of  swamps,  and  sometimes  make  thick  beds  which 
are  very  porous,  and  irregular  in  thickness  and  texture,  called 
calcareous  tufa,  and  also  travertine.  On  Gardiner's  Eiver,  in 
the  Yellowstone  Park,  at  the  summit  of  the  Rocky  Mountains, 
such  deposits  are  forming,  and  the  river  is  thus  made  into 
a  series  of  waterfalls.  But  such  beds  of  limestone  are  of 
even  less  extent  and  importance  than  igneous  rocks.  None 
of  the  great  limestones  of  the  world  were  thus  made. 

Waters  often  hold  traces  of  silica  in  solution,  especially 
if  hot  and  alkaline,  and  deposit  it  again,  making  siliceous 
beds  and  petrifactions.  Some  facts  on  this  point  are  men- 
tioned beyond,  among  the  eifects  of  heat  in  rock-making. 
Cold  water  seldom  deposits  silica  unless  where  there  are 
the  remains  of  siliceous  infusoria,  as  mentioned  on  page  38. 

3.  Rocks  made  by  the  mechanical  agency  of  waters  and 
winds,  exclusive  of  limestones.  —  Par  the  larger  part  of  rocks 


MAKING  OF  ROCKS.  25 

are  fragmental  rocks ;  that  is,  they  are  rocks  made  out  of 
fragments  of  older  rocks.  The  finest  mud  or  clay  consists 
of  fragments  of  rock-material,  and  hence  a  shale  —  a  rock 
made  from  fine  mud  or  clay  —  is  a  fragmental  rock  as 
much  as  a  sandstone  or  conglomerate. 

A  large  part  of  the  fragments  —  or  the  sand,  pebbles, 
mud  - —  were  made  by  the  wearing  action  of  moving  waters ; 
and  hence  such  material  is  called  detritus,  from  the  Latin, 
meaning  worn  out.  The  agency  of  greatest  effects  and  long- 
est action  in  past  time  has  been  the  ocean;  that  of  next 
importance,  rivers ;  that  next,  winds.  But,  preparatory  for 
these  agencies,  the  air,  moisture,  and  the  sun's  heat  have 
been  always  quietly  at  work  giving  aid  in  the  reduction  of 
rocks  to  fragments  or  grains;  and  thus  the  ocean,  rivers,  and 
winds  have  found  much  loose  material  ready  for  them,  in- 
stead of  being  left  to  make  all  that  was  required  for  their 
work  in  rock-making. 

The  sand,  gravel,  and  mud  or  clay  of  which  rocks  have 
been  made  were  in  general  deposited  as  a  sediment  from  the 
waters  of  the  ocean  or  rivers,  as  will  be  explained  further 
on ;  and  hence  sandstones,  conglomerates,  and  shales  are  called 
sedimentary  rocks. 

4.  Rocks  made  mainly  or  wholly  of  organic  remains,  that 
is,  of  the  remains  of  plants  or  animals,  —  (1)  The  great  lime- 
stones of  the  world  are  of  this  origin ;  also  (2)  some  sili- 
ceous deposits;  and  (3)  the  coal-beds  and  peat-beds  of  the 


26  CAUSES  AND  THEIR  EFFECTS. 

world.  Many  sandstones  and  shales  contain  more  or  less  of 
such  remains.  Plants,  shells,  and  other  distinguishable  relics 
of  living  species  found  in  rocks  are  called  fossils,  or  organic 
remains.  They  are  sometimes  called  also  petrifactions,  which 
means  made  of  stone  ;  but  not  always  rightly  so,  for  most 
fossils  consist  of  the  same  material  essentially  that  they  had 
when  in  the  living  species.  Wood  is  sometimes  changed  to 
stone;  and  this  is  then  a  true  petrifaction. 

5.  Metamorphic  Rocks.  —  Fragmental  rocks,  such  as  sand- 
stones, shales,  and  conglomerates,  and  also  limestones,  have 
sometimes  been  altered  (or  metamorphosed),  over  regions  of 
great  extent,  to  crystalline  rocks,  such  as  granite,  gneiss, 
mica  schist,  granular  limestone  or  architectural  marble;  and 
these  crystalline  rocks  are  hence  called  metamorphic  rocks, 
the  word  metamorphic  meaning  altered. 

In  describing  these  methods  of  making  rocks  the  following 
order  is  here  adopted  :  — 

1.  The  ways  in  which  plants  and  animals   have  contributed 
to  rock-making. 

2.  The  results  from  the  quiet  working  of  air  and  moisture. 

3.  The  work  of  winds. 

4.  The  work  of  rivers. 

5.  The  work  of  the  ocean. 

6.  The  work  done  by  ice. 

7.  The  work  of  heat. 


LIMESTONE  ROCKS  OE  ORGANIC  ORIGIN. 


I.   Ways  in  which  Plants  and  Animals  have  contributed 
to  Rock-making. 

1.    Making  of  Limestones. 

The  animal  relics  that  have  contributed  most  to  limestones 
are  shells,  corals,  crinoids,  and  foraminifers.  These  are  secre- 
tions of  animals,  that  is,  stony  portions  of  the  body,  either 
made  internally  in  the  same  manner  as  the  bones  of  a  dog  are 
made,  or,  like  a  shell,  made  externally  as  a  covering  for  the 
animal.  When  the  animal  dies,  the  relics  pass  to  the  mineral 
kingdom  and  are  used  in  rock-making ;  and,  as  stated  above, 
nearly  all  the  limestones  have  thus  been  made. 

Corals  and  crinoids  are  exclusively  oceanic  species  of  ani- 
mals ;  but,  while  this  is  true  also  of  most  shells  and  fora- 
minifers, there  are  some  kinds  that  nourish  in  fresh  waters, 
and  among  shells  some,  like  the  snail,  live  over  the  land. 

Shells  are  the  secretions  of  animals  related  to  the  oyster, 
clam,  snail,  and  cuttle-fish,  —  animals  that  have  a  soft  fleshy 
body,  and  hence  are  called  Mollush,  from  the  Latin  mollis, 
soft.  The  shells  serve  to  protect  the  soft  body  and  give  it 
rigidity. 

Coral  is,  for  the  most  part,  the  secretion  of  polyps,  the 
most  flower-like  of  animals,  and  it  is  an  internal  secretion. 
One  of  the  branching  corals,  covered  over  (one  branch  ex- 
cepted)  with  its  numerous  little  flower-animals,  is  represented 
in  Pig.  13.  Branching  corals  of  this  nature  are  common  in  the 


28 


MAKING  OF  ROCKS. 


tropical  Pacific,  and  are  called  Madrepores.  Another  kind,  mas- 
sive instead  of  branching,  is  shown  in  Eig.  14.  The  whole 
surface  is  a  surface  of  flower-animals  or  polyps;  in  reference 
to  its  star-like  cells,  this  kind  is  called  an  Astraa.  The 

Fig.  13. 


Madrepora  aspera  D. 


expanded  animals  (only  part  of  which  in  the  figure  are  in  this 
state)  are  like  flowers  also  in  their  bright  colors.  The  little 
petal-like  arms  (tentacles),  in  Pig.  13,  are  tipped  with  emerald- 
green,  in  the  living  state;  and  some  Astrseas  are  purple  or 


LIMESTONE  ROCKS  OE  ORGANIC  ORIGIN. 


Fig.  14. 


Fig.  15. 


Astraea  pallida  D. 

crimson  with  an  emerald  centre,,  and  others  have  other  bright 

tints.     "While  so  much  like  flowers  in  appearance,  polyps  are 

wholly  animal   in  nature.     Each    polyp   has  a    mouth   at   the 

centre   above,   as   shown  in  Pig.  14; 

and    it    eats    and    digests    like    other 

animals.      Another   kind    of   coral    is 

represented   in    Fig.    15,   without   the 

animal;   it  shows  the  radiating   plates 

in  the  cup-shaped  cavity  at  top.     Still 

another,  somewhat  larger,  elliptical  in 

shape  instead  of  cylindrical,  and  in  the 

living  state,  is  presented  in  Fig.   16. 

The  mouth   is  a   very   long  one,  and 

the  arms  or  tentacles  which  serve  to  push  in  the  prey  it  cap- 


Thecocyathus   cylindraceua 
Pour-tales. 


30  MAKING  OF  ROCKS. 

tures  are  also  long.     It  owes  much  of  its  power  of  capturing 
to  the  stinging  qualities  of  these  tentacles. 

The  arrangement  of  the  tentacles  of  a  polyp  around  a 
centre,  and  also  that  of  the  plates  inside  of  the  coral  cup,  is 
radiate;  and  hence  Polyps,  like  some  other  kinds  of  life,  are 
called  Radiate  animals. 

Tig.  1C. 


Flabellum  pavoninum. 

Crinoids.  —  Crinoids  also  are  flower-like  animals,  and  Radi- 
ates. They  were  once  exceedingly  abundant  in  the  seas  of  the 
world,  but  now  are  rarely  to  be  found.  Two  of  the  kinds  are 
represented  in  Figs.  17  and  18,  the  first  an  ancient  species, 
and  the  second  a  modern  one  from  the  seas  of  the  "West  Indies. 
The  arms  above  are  arranged  around  a  centre  like  the  petals 
of  a  flower,  and,  like  them,  they  may  be  opened  out  wide  or 
closed  up  so  as  to  look  like  a  bud;  and  this  the  animal  does 
at  will.  Below  the  radiating  head-bearing  part  there  is  a 
stem,  sometimes  a  foot  or  more  long,  which,  if  the  animal  is 


LIMESTONE  ROCKS  OF  ORGANIC  ORIGIN. 


31 


alive,  is  planted  below  on  the  solid  rock,  or  in  the  mud  of  the 
sea-bottom.  Crinoids  differ  in  many  respects  from  polyps. 
One  point  is  this :  the  coral  which  a  polyp  makes  is  all  one 

Figs.  17,  18. 


Crinoids. 

Fig.  17,  Zeacrinus  elegans  ;  18,  Pentacrinus  caput-Medusae,  now  living  in  the  West  Indies;  a~d,  calcareous 
disks  or  plates  of  the  stem,  showing  their  s-sided  form. 

piece,  whether  massive  or  branching;  while  the  stony  secretion 
of  the  crinoid  is  in  multitudes  of  pieces.  The  stem  is  a  pile 
of  little  disks  often  circular  and  looking  like  button-moulds, 
as  in  Eig.  17;  but  sometimes  5-sided,  as  in  Pigs.  18  a,  b,  c,  d, 
showing  some  of  the  forms.  The  arms  also  are  made  up  of 
stony  pieces.  The  cross-lines  on  the  arms  in  the  above  figures 
indicate  the  number  of  pieces  of  which  each  is  made.  The 
pieces  are  held  together  by  animal  membrane  as  long  as  the 
animal  lives ;  but  when  it  dies,  the  pieces  usually  fall  apart, 
and  are  scattered  by  the  moving  waters. 


MAKING  OF  ROCKS. 


Foraminifers.  —  Foraminifers  are  made  by  the  simplest  of 
all  animals,  and  very  minute  kinds,  —  animals  that  have  no 
organs  of  sense,  and  in  general  not  even  a  mouth  to  eat  with. 
When  a  particle  of  the  desired  food  touches  the  body,  and  is 
perhaps  held  there  by  its  power  of  stinging,  that  part  of  the 
body  begins  to  be  depressed,  and  continues  to  sink  inward 
until  the  food  is  in  a  cavity  inside  made  for  the  occasion; 
then  the  food  is  digested,  and  any  part  of  it  not  digested  is 
thrown  out  by  restoring  the  body  to  its  former  state.  Some 


Rhizopods. 

Fig.  19,  Orbulina  universa ;  20,  Globigerina  rubra  ;  21,  Textilaria  globulosa  ;  22,  Rotalia  globulosa  ;  22  a, 
side-view  of  Rotalia  Boucana  ;  23,  Grammostomum  phyllodes ;  24,  Frondicularia  annularis ;  25,  Triloculina 
Josephina  ;  26,  Nodosaria  vulgaris  ;  27,  Lituola  nautiloides  ;  28  a,  Flabellina  rugosa ;  29,  Chrysalidina 
gradata ;  30  a,  Cuneolina  pavonia ;  31,  Nuuimulites  nummularia  ;  32  a,  b,  Fusulina  cylindrica. 

of  the  shells  are  represented  much  enlarged,  excepting  the 
last  three,  in  Figs.  19  to  32.  Many  of  these  animals  have 
the  faculty  of  extending  out,  at  will,  feelers  over  the  body 
that  are  a  little  root-like,  and  hence  they  are  called  Rhizoporfs, 
from  the  Greek  for  root-like  feet.  An  enlarged  view  of  one  of 


LIMESTONE  ROCKS  OF  ORGANIC  ORIGIN.  33 

the  species,  with  the  fibre-like  arms  extended,  is  shown  in  Fig. 
33.  All  of  the  shells  above  figured,  excepting  the  last  three, 
are  no  larger  than  the  finest  grains  of  sand ;  and  yet  they 
contain  .a  number  of  cells,  each  of  Fig.  33. 

which  corresponds  to  a  separate  one 
of  the  Rhizopod  animals. 

Kg.  31  is  a  large  foraminifer 
shaped  like  a  coin,  and  the  Latin 
for  coin,  nummus,  suggested  for  it 
the  name  it  bears,  —  a  Nummulite. 

Shells,  corals,  crinoids,  and  fora-  Eotaiia  veneu. 

minifers  consist  almost  solely  of  carbonate  of  lime,  —  the 
material  of  limestone ;  and  hence  their  consolidation  makes 
limestone.  Shells,  corals,  and  crinoids  are  usually  more  or 
less  ground  up  under  the  action  of  the  waves  or  currents 
of  the  ocean,  and  thus  reduced  to  fragments  or  sand,  before 
they  are  consolidated.  Much  coral  limestone  of  existing  seas 
—  the  rock  of  coral  reefs  —  shows  no  trace  of  the  corals  of 
which  it  was  made,  because  all  were  ground  by  the  aid  of  the 
waves  and  currents  to  a  coral  sand  or  coral  mud  before  con- 
solidation. But  in  other  cases  the  rock  contains  fragments  of 
the  corals  or  crinoids,  and  sometimes  entire  specimens.  Eig. 
34  shows  the  aspect  of  a  crinoidal  limestone  when  the  crinoidal 
remains  are  not  wholly  ground  up;  the  disks  and  cylinders 
are  portions  of  the  stems  of  the  crinoids.  The  coral  reefs 
of  the  Pacific  are  coral-made  limestones,  and  some  of  them 
2*  c 


MAKING  OF  ROCKS. 


are  hundreds  of  square  miles  in  area  and  many  hundreds 
of  feet  in  thickness. 

Foraminifers   are  so  minute  that  they  need  no  grinding  in 

order  to  make  a  fine-grained 
rock.  They  live  in  sea- 
waters  of  all  depths,  and 
are  especially  abundant  over 
the  sea-bottom  down  to  a 
depth  of  twelve  or  fifteen 
thousand  feet,,  as  has  been 
proved  by  soundings  in  the 
Atlantic  between  Ireland 
and  Newfoundland,  and 
elsewhere.  Chalk  is  made 

mainly  of  foraminifers,  and  was  of  deep-water  origin ;  and 
chalk  is  now  making,  and  has  been  through  ages  past,  over 
the  bottom  of  the  ocean. 

There  are  also  some  plants,  of  the  order  of  Sea-weeds,  that 
secrete  lime,  and  which  have  thereby  contributed  to  rock-mak- 
ing. Among  these  are  included  (1)  coral-making  plants,  called 
Nullipores,  —  so  named  from  the  fact  that,  while  looking  like 
corals,  they  have  no  pores  or  cells;  (2)  Corallines,  which  are 
related  to  Nullipores,  but  have  delicate  jointed  stems;  (3) 
CoccolitJiSj  which  are  microscopic  calcareous  disks,  very  abun- 
dant over  some  parts  of  the  ocean's  bottom  and  occurring  also 
in  shallower  waters. 


Crinoidal  Limestone. 


SILICEOUS  ROCKS  OF  ORGANIC  ORIGIN. 


35 


2.    Making  of  Siliceous  Rocks  or  Masses. 

Some  of  the  minutest  and  simplest  of  plants  and  animals 
make  stony  secretions  of  silica  instead  of  carbonate  of  lime, 
and  hence  form  out  of  their  stony  secretions  beds  of  silica 
instead  of  beds  of  limestone.  Although  minute,  often  requir- 
ing a  high  microscopic  power  even  to  see  them,  such  species 
have  thus  been  large  contributors  to  rock-making  through  all 
geological  history.  Many  of  them  are  remarkable  for  their 
beauty  of  form  and  texture. 

The  plants  here  included  are  called  Diatoms.  Nearly  all 
are  too  minute  to  be  distinguished 
without  a  lens.  Some  of  the  forms 
are  shown,  .  highly  magnified,  in  the 
annexed  figures,  35-40.  They  are 
strange  forms  for  plants,  and  still 
are  known  to  be  of  this  king- 
dom of  life.  They  have  lived  in 
such  numbers  over  the  bottoms  of 

shallow 


Figs< 


Diatoms  highly  magnified. 

and      SeaS,     Fig.   35,   Pinnularia   peregrina,    Richmond, 
Va.  ;  36,  Pleurosigma  angulatum,  id.  ;  37, 

that    the    infinitesimal    shells    have     %5^fS^\£!SZ 

same  ;    39,   Grammatophora  marina,  from 

SOmetimeS        made        beds        SCOreS        Of       the  salt  water  at  Stonington,  Conn.  ;   40. 

Bacillaria  paradoxa,  West  Point. 

yards   in   thickness.      The    material 

of  such  beds  looks  like  the  finest  of  chalk.  Owing  to 
the  hardness  and  extreme  fineness  of  the  grains,  it  was  used 
as  a  polishing  powder  long  before  it  was  discovered  that 
each  particle  was  the  secretion  of  a  microscopic  water-plant. 


36 


MAKING  OF  ROCKS. 


It  is  obtained  from  the  bottoms  of  many  marshes,  and  sold 
for  polishing;  and  the  packages  in  the  shops  from  beds  in 
Maine  are  labelled  Silex.  A  bed  of  great  extent  in  Virginia, 


Fig.  41. 


Richmond  Infusorial  Earth. 

a,  Pinnularia  peregrina ;  6,  c,  Odontidium  pinnulatum ;  d,  Grammatophora  marina  ;  e,  Spongiolithis  appen- 
diculata  ;f,  Melosira  sulcata  ;  g;  transverse  view,  id.  ;  h,  Actinocyclus  Ehrenbergii ;  z,  Coscinodiscus  api- 
culatus  ;  j,  Triceratium  obtusum  ;  k,  Actinoptychus  undulatus ;  /,  Dictyocha  crux  ;  »*,  Dictyocha  ;  «,  frag- 
ment of  a  segment  of  Actinoptychus  senarius  ;  o,  Navicula ;  p,  fragment  of  Coscinodiscus  gigas. 

near  Richmond,  is  in  some  places  thirty  feet  thick ;  and  a  little 
of  the  dust,  under  the  microscope  of  Ehrenberg  of  Berlin, — 


SILICEOUS  ROCKS  OE  ORGANIC  ORIGIN. 


37 


Figs.  42-44. 


who  first  made  known  the  nature  of  these  polishing  powders,, 
—  presented  the  appearance  shown  in  the  foregoing  figure. 
These  forms  were  all  in  the  field  of  his  microscope  at  one 
time.  Nearly  every  particle  is  a  Diatom  or  a  fragment  of 
one.  Some  beds  near  Monterey,  in  California,  have  a  thick- 
ness exceeding  fifty  feet. 

Among  animals  making  siliceous  shells,  the  following  are 
examples.  (1)  A  kind  illustrated  in  Pigs.  42-44,  related 
to  the  foraminifers,  the 
animals  being  Rhizopods, 
but  differing  in  their 
forms,  and  in  secreting 
silica  instead  of  lime. 

(2)  Most  Sponges,  for 
sponges  are  animal  in  na- 
ture.  Ordinary  sponges 

are  made  of  horn-like  fibres;  but  in  the  living  state  these 
fibres  are  covered  thinly  with  an  animal  coating  which  is  in 
reality  a  layer  of  microscopic  animals  hardly  higher  in  grade 
than  Rhizopods.  In  a  large  part  of  them  these  horny  fibres 

Fig.  45. 


Siliceous  spicules  of  Sponges. 

are  bristled  with  minute  spicules  of  silica  of  various  forms. 
A  few  of  these  forms  are  shown  in  Figs.  45  a  —  k.  Some  of 
the  oblong  pieces  or  fragments  in  Fig.  41,  page  36,  are  spi- 
cules of  ancient  sponges. 


38  MAKING  OF  ROCKS. 

Other  sponges  consist  wholly  of  fibres  of  transparent  silica, 
excepting  a  thin  coating  of  animal  material.  One  of  these  sili- 
ceous sponges  from  the  bottom  of  the  East  India  seas  is 
represented  in  Pig.  46,  but  only  half  the  natural  size.  The 
extreme  delicacy  of  the  structure  might  hardly  be  inferred 
from  the  figure;  for  the  sponge  looks  as  if  made  of  spun 
glass,  and  as  if  too  fragile  to  be  handled.  Such  siliceous 
sponges  are  common  over  the  bottom  of  the  ocean,  and  at 
various  depths  below  the  reach  of  the  waves,  whose  violence 
they  could  not  withstand. 

The  flint  of  the  world,  or  hornstone  as  the  most  of  it  is 
called  (page  4),  is  nearly  pure  silica  (or  quartz),  and,  like 
quartz,  it  scratches  glass  easily.  It  is  found  imbedded  in 
limestones  and  other  rocks.  It  has  been  made  for  the  most 
part  out  of  diatoms  and  spicules  of  sponges,  and  without  any 
unusual  degree  of  heat.  This  fact  shows  that  such  deposits, 
when  under  water,  may  be  partly  dissolved  by  the  cold  waters, 
and  then  consolidated  without  any  external  aid  beyond  that 
afforded  by  the  saline  ingredients  of  the  waters.  By  the  same 
means  shells  and  other  fossils  have  often  been  changed  to 
quartz,  or  have  undergone  a  true  petrification. 

Besides  shells,  corals,  crinoids,  forammifers,  diatoms,  and 
sponges,  relics  of  various  other  kinds  of  animals  are  con- 
tained in  rocks  or  have  contributed  to  their  material.  These 
are  the  harder  parts  of  Worms,  Insects,  Spiders,  Centipedes, 
and  of  various  Crustaceans  (among  these  last,  Shrimps,  Crabs, 


Fig.  46,  Euplectella  speciosa,  or  Glass  Sponge. 


40  MAKING  OF  ROCKS. 

and  inferior  kinds) ;  the  bones  and  scales  of  Fishes  and  Rep- 
tiles ;  the  bones  and  occasionally  the  feathers  of  Birds ;  the 
bones  of  Quadrupeds  of  various  kinds,  and  remains  of  various 
other  forms  of  life ;  and,  besides,  the  trades  of  animals,  from 
those  of  Worms  and  Insects  to  those  of  Quadrupeds  and  Man. 

The  living  species  of  the  globe  that  have  contributed  most 
to  rocks  are  those  of  the  waters,  because  rocks  are  mainly 
of  aqueous  origin ;  and  chiefly  marine  species,  because  the 
greater  part  of  rock-making  has  been  performed  by  the  ocean. 

Oceanic  life  is  in  greatest  profusion  along  the  shallow 
waters  off  shore,  down  to  a  depth  of  a  hundred  feet,  — 
the  corals  making  coral  reefs  in  our  present  seas  not  living 
at  a  greater  depth  than  this.  But  there  is  abundant  life  at 
greater  depths,  and  even  over  the  ocean's  bottom  down  to 
about  15,000  feet.  Crabs  with  good  eyes  have  been  obtained 
from  the  sea-bottom  at  a  depth  of  5,000  feet;  lobsters  without 
eyes  at  a  depth  of  5,000  to  12,000  feet;  and  a  few  living  mol- 
lusks  from  a  depth  exceeding  12,000  feet.  Besides  these  species, 
there  are  through  all  these  depths  scattered  Corals,  Crinoids,  and 
delicate  siliceous  Sponges  related  to  that  figured  on  page  39. 
But  Rhizopods  are  the  most  abundant  species  (page  32),  and  with 
them  there  are  the  minutest  and  simplest  of  plants,  Diatoms  and 
Coccoliths. 

3.    Making  of  Peat-beds. 

In  marshy  areas,  where  spongy  mosses  of  the  genus  Sphag- 
num are  growing  luxuriantly  along  with  other  water-loving 


PEAT-BEDS.  41 


plants  small  and  large,  and  some  kinds  that  can  stand  the 
water,  but  would  thrive  better  were  it  drier,  there  are  always 
deposits  of  leaves  and  stems  and  other  remains  of  plants 
forming  under  the  water.  The  moss,  which  is  the  chief  plant 
in  the  increasing  deposit,  has  the  faculty  of  dying  below 
while  growing  above;  and  thus  its  dead  stems  may  be  many 
yards  long,  while  the  living  part  at  top  is  only  six  inches 
or  so.  The  small  plants  and  shrubs,  and  the  trees,  if  such 
there  be,  shed  their  leaves  and  fruit  annually,  and  these  fall 
into  the  water.  Annual  plants  die  each  year,  and  their  stems 
are  buried  with  the  leaves.  All  the  plants,  the  mosses  ex- 
cepted,  sooner  or  later  die,  and  thus  branches  and  trunks  are 
added  at  times  to  the  accumulation  in  progress.  Birds  and 
quadrupeds  may  add  their  bones,  and  insects,  with  the  vari- 
ous inferior  kinds  of  life  in  such  places,  may  become  min- 
gled with  the  other  relics. 

The  materials  of  plants  buried  under  water  undergo  a  kind 
of  smothered  combustion.  They  become  black,  then,  below, 
are  reduced  to  a  pulpy  state,  or  rarely  to  an  imperfect  coal; 
and  the  mass  thus  altered  constitutes  what  is  called  peat. 

Dry  woody  material  consists,  one  half  of  carbon,  or  the 
main  constituent  of  charcoal,  along  with  two  gases,  oxygen 
and  hydrogen;  and  in  the  change  the  proportion  of  the  gases 
to  the  carbon  is  diminished  about  one  fifth.  The  black  color 
—  one  result  of  the  change  —  is  due  to  the  carbon,  as  in  the 
case  of  the  black  color  of  soils,  many  muds,  and  black  clayey 
and  calcareous  rocks. 


MAKING  OE  ROCKS. 


The  bed  of  peat  sometimes   increases   until  it   is   scores  of 

•   yards   in   depth.     Ireland  is   noted  for  its  peat  swamps  ;   the 

"mosses/'  as  they  are  called,  of  the  Shannon,  are  fifty  miles 

long  and  two   to   three  broad.      Peat    swamps    are   common 

over  all  continents   out   of  the  tropics.     The  Dismal  Swamp 

<•    in  North  Carolina  is   a  peat   swamp    from    one   end    to    the 

other;  and  no  one  has  yet  ascertained  the  depth  of  the  peat. 

The  world  has  had  its  peat  swamps  in  all  ages  since  the 
first  existence  of  abundant  terrestrial  vegetation;  and  they 
are  the  sources  of  all  its  coal-beds,  each  coal-bed  having 
been  first  a  peat-bed.  But  the  kinds  of  plants  concerned 
have  varied  with  the  successive  ages. 

2.    Quiet  Work  of  Air  and  Moisture. 

When  rocks  are  wholly  under  water,  whether  it  be  salt 
or  fresh  water,  they  are  generally  protected  from  decay.  But 
if  above  the  water,  so  that  air  as  well  as  moisture  has 
free  access,  nearly  all  become  altered,  and  many  crumble  to 
sand  or  change  to  clayey  earth.  Blocks  of  some  kinds  of 
sandstone  that  would  answer  well  for  under-water  structures, 
when  left  exposed  to  the  air  for  a  few  years  fall  to  pieces 
or  peel  off  in  great  concentric  layers.  Crystalline  limestone 
(white  and  clouded  marble)  in  many  regions  covers  the  sur- 
face with  marble  dust  from  its  decay.  Gneiss  and  nlica 
schist  are  among  the  durable  rocks  ;  and  yet  much  of  the 
gneiss  and  mica  schist  of  the  world  undergoes  slow  alter- 


QUIET  WORK  OF  AIR  AND  MOISTURE.  43 

ation,  so  that  in  some  regions  they  are  rotted  down  or  have 
become  soft  earth  or  a  gravel  to  a  depth  of  fifty  or  a  hun- 
dred feet,  and  even  two  or  three  hundred  in  tropical  coun- 
tries. This  is  the  amount  of  decomposition  produced  in  those 
places  through  a  very  long  period  of  time,  perhaps  the  whole 
time  from  the  epoch  of  their  elevation  above  the  ocean. 
But  it  is  no  measure  of  the  amount  that  would  have  taken 
place  if  the  decayed  portion  had  been  removed  as  it  was 
formed,  as  has  often  happened;  for,  in  that  case,  alter- 
ation would  have  proceeded  with  greater  rapidity  because  of 
the  freer  access  of  air  and  moisture. 

The  granite  hills  are  often  thought  of  as  an  example  of 
the  everlasting,  as  far  as  anything  is  so  on  the  earth.  But, 
while  there  is  granite  that  is  an  enduring  building- stone, 
a  large  part  of  the  granite  of  the  world  becomes  so  changed 
on  long  exposure  that  the  plains  and  slopes  around  are 
thence  deeply  covered  with  the  crumbled  rock,  and  great 
masses  may  be  shivered  to  fragments  by  a  stroke  of  a  sledge. 
Many  granitic  elevations  over  the  earth's  surface  have  dis- 
appeared beneath  their  own  debris. 

Much  trap-rock  is  as  firm  as  the  best  granite.  But  other 
kinds  are  rotted  down  to  a  depth  of  many  feet  or  yards,  and 
sometimes  only  here  and  there  a  ledge  shows  itself  above  the 
ground  as  the  remains  of  ranges  of  hills.  Even  the  most 
solid  trap,  where  exposed  to  the  elements,  has  a  decomposed 
outer  layer,  or  is  weathered,  as  the  change  is  called.  This 


44  MAKING  OF  ROCKS. 

crust  is  often  but  a  line  or  two  deep  and  has  everywhere 
the  same  depth  over  blocks  of  like  kind.  But  this  depth 
is  constant,,  because,  as  the  elements  eat  inward,  there  is  as 
gradual  a  loss  of  the  altered  grains  over  the  outer  surface. 

Thus  invisible  agencies  are  producing  the  slow  destruc- 
tion of  the  exposed  parts  of  nearly  all  the  rocks  of  the 
globe,  even  to  the  tops  of  the  lofty  mountains.  The  firmer 
kinds  of  slates  (argyllite),  some  hard  conglomerates  and 
gneisses,  and  the  compact  limestones  are  the  rocks  that  defy 
the  elements  most  successfully. 

In  this  way  rocks  have  been  prepared  for  the  rougher 
geological  work  carried  on  by  moving  water  and  ice ;  and 
through  the  same  means  the  earth  or  soil  of  the  world  has 
to  a  large  extent  been  made. 

This  quiet  work  of  air  and  moisture  is  really  chemical 
work ;  and  it  is  mostly  performed  through  the  chemical 
action  of  two  ingredients  present  in  them,  —  carbonic  acid 
and  oxygen.  Other  agencies  aid  in  this  slow  destruction,  as 
explained  on  pages  beyond. 

3.    The  Work  of  Winds. 

Winds,  or  moving  air,  carry  sands  from  one  place  to 
another,  and  wherever  the  earth's  surface  is  one  of  dry  sand, 
and  the  winds  blow  strongest  and  longest  in  one  direction, 
great  accumulations  of  sand  are  made.  Even  when  the  win- 
dows of  a  house  in  a  city  are  ordinarily  kept  closed,  the  dust 


WORK  OF  WINDS.  45 


will  get  in.  The  west  winds  have  driven  the  sands  of  the 
Desert  of  Sahara  over  parts  of  Egypt,  and  the  ruins  of  an- 
cient cities  have  thus  been  buried. 

Sea-shores  are  often  regions  of  sand,  owing  to  the  work  of 
the  waves.  The  heavy  winds  take  up  the  loose,  dry  sands  and 
carry  them  beyond  the  beach,  to  make  ranges  of  sand-hills, 
often  20  to  30  or  more  feet  high.  Thence  the  hills  frequently 
travel  inland,  through  the  same  means,  sometimes  burying  for- 
ests, as  on  the  west  coast  of  Michigan,  sometimes  overwhelm- 
ing villages,  as  in  England  and  France,  leaving  at  times  only 
the  top  of  a  church-spire  to  mark  the  site. 

The  stratification  of  a  hill  of  drifted  sands  is  so  peculiar 
that  it  is  easy  to  tell  when  sand-rocks  have  been  formed 
through  the  agency  of  the  winds.  Fig.  47  represents  a  part  of 
a  section  observed  in  the  Pictured 

Fig.  47. 

Hocks  on  the  south  shores  of  Lake 
Superior.  The  layers  dip  in  many 
directions.  Such  a  structure  is  ow- 
ing to  the  accidents  to  Which  the  Part  of  a  section  of  a  drift  sand-hill, 

showing  the  stratification. 

sand-hills   are   exposed.      A   heavy 

storm  —  perhaps  aided  by  heavy  waves  at  high  tide  —  often 
carries  away  part  of  a  hill.  Then  the  winds  build  it  up  anew, 
putting  the  successive  drifts  —  which  make  the  successive  lay- 
ers —  over  the  new  surface,  differing  much  from  the  first  in  its 
slopes.  The  hill  suffers  from  another  storm,  and  is  again  built 
up  during  the  period  of  quieter  weather  that  follows.  This 


46  MAKING  OF  ROCKS. 

may  take  place  many  times.     The  result  is  the  kind  of  irregu- 
larity of  stratification  illustrated  in  the  cut. 

Sands  carried  by  winds  over  rocks  often  wear  the  surfaces 
deeply,  as  noticed  in  the  Colorado  desert,  in  the  Grand  Traverse 
region  near  Lake  Michigan,  and  elsewhere.  This  agency  has 
scoured  out  gorges,  shaped  and  undermined  bluffs,  and  worn 
away  rocks,  in  the  dry  parts  of  the  Eocky  Mountain  region. 
Man  has  taken  the  hint,  and  now  uses  sand  driven  by  steam 
to  etch  on  glass  and  to  carve  granite  and  other  rocks. 

4.    The  Work  of  Fresh  Waters. 

Eunning  water  is  at  work  universally  over  a  continent 
wherever  there  is  a  slope  to  produce  movement,  and  the  clouds 
yield  rain;  and  it  acts  with  greatest  energy  where  the  slope  is 
greatest,  or  about  high  hills  and  mountains. 

The  waters  of  the  rains,  mist,  and  dew  about  the  mountain- 
tops  descend  in  drops  and  rills,  and  then  gather  into  plunging 
streamlets  and  torrents ;  the  many  torrents  combine  below  into 
larger  streams;  and  these,  from  over  a  wide  region,  unite  to 
make  the  great  rivers.  The  Mississippi  has  its  arms  reaching 
westward  and  northward  to  various  summits  in  the  Eocky 
Mountains,  and  eastward  to  the  Appalachians;  and  its  great- 
ness is  owing  to  the  vast  breadth  of  the  area  it  drains.  Not 
only  mountains,  but  every  small  elevation  over  a  land,  and 
even  its  little  slopes,  have,  when  it  rains,  their  rills  combining 
into  torrents,  and  these  into  larger  streams,  which  flow  off  to 
join  some  river. 


WORK  OF  FRESH  WATERS.  47 

The  waters  of  the  clouds  no  sooner  drop  to  the  ground  than 
they  begin  to  work,  tearing  off  and  carrying  away  grains  of 
earth  from  the  rocks  or  slopes.  The  stronger  rills  act  in 
this  way  with  much  greater  effect;  and  the  torrents  move 
stones  as  well  as  earth.  This  work  over  the  larger  part  of  a 
country  may  be  almost  wholly  suspended  in  the  dry  season. 
But  when  the  rains  set  in  the  surface  is  alive  with  its  work- 
ers, small  and  great.  Torrents  become  increased  immensely  in 
depth  and  force,  and  earth  and  often  rocks  are  torn  up  and 
borne  along  in  vast  quantities. 

The  more  rapid  the  flow  of  the  water  the  coarser  the  de- 
tritus it  can  transport;  and  as  a  stream  slackens  its  rate  the 
coarser  material  falls  to  the  bottom,  leaving  only  the  finer  to 
be  carried  on.  Thus  the  large  stones  and  then  the  smaller 
will  drop  as  the  torrent  becomes  less  and  less  violent ;  but  the 
earth  and  gravel  may  be  borne  on  to  the  rivers;  and  these,  in 
their  times  of  flood,  may  carry  a  large  part  of  the  burden  of 
earth  to  the  ocean.  Under  such  a  rough-and-tumble  move- 
ment stones  are  worn  to  earth  and  gravel,  and  in  this  pulver- 
ized state  they  may  continue  the  journey  seaward.  A  single 
heavy  rain-storm  has  sometimes  so  filled  the  narrow  gorges  of 
a  mountain  that  vast  deluges  of  water,  rocks,  gravel,  and  trees 
have  swept  down,  carrying  away  houses  and  spreading  desola- 
tion over  the  plains  below. 

Through  the  wearing  effect  of  rivers  and  their  tributaries, 
reaching  to  every  part  of  a  continent,  the  mountains,  ever 


48  MAKING  OF  ROCKS. 

since  their  first  emergence,  have  been  on  the  move  to  the 
ocean,  and  we  cannot  judge  of  their  former  height  from  what 
now  exists. 

The  process  of  erosion  is  often  called,  in  geology,  degra- 
dation, because  mountains  and  hills  are  made  low  by  it;  and 
denudation,  because  it  removes  their  exterior. 

The  average  amount  of  sediment  annually  carried  to  the 
borders  of  the  Gulf  of  Mexico  by  the  Mississippi  River  has 
been  stated  to  be  812,500,000,000  pounds,  or  enough  to  make 
a  pyramid  a  square  mile  at  base  over  700  feet  in  height. 
This  material  is  deposited  about  the  mouth  of  the  river,  and 
is  gradually  extending  it  farther  and  farther  into  the  Gulf. 
The  fine  sediment  of  rivers  settles  much  more  rapidly  in  salt 
water  than  in  fresh,  and  this  is  one  reason  why  this  material 
is  prevented  from  being  carried  off  to  the  deep  ocean. 

The  great  area  about  the  mouth  of  a  large  river  over  which 
these  deposits  are  distributed  is  usually  intersected  by  chan- 
nels, and  constitutes  what  is  called  a  delta.  Fig.  48  represents 
the  delta  of  the  Mississippi. 

The  channel  of  the  river  extends  far  into  the  Gulf  of 
Mexico,  and  terminates  in  several  mouths.  The  delta  stretches 
northward  nearly  to  the  mouth  of  Red  Eiver,  and  has  an  area 
of  about  12,300  square  miles.  The  waves  and  currents  of  the 
Gulf  act  with  the  currents  of  the  river  in  the  deposition  of 
the  sediment. 

The  Mississippi  is  an  example  of  what  all  rivers  are  doing, 


WORK  OF  FRESH  WATERS. 


49 


each  according  to  its  ability.     Some  carry  their  detritus  to  lakes, 
to  extend  their  shores,  and  aid  in  filling  them.     But  much  of 


the  detritus  is  left  on  the  various  river-flats,  and  this  part  is 
called  alluvium.     Again,  a  large  part  reaches  the  ocean,  and 
3  i> 


50  MAKING  OE  ROCKS. 

is  distributed  along  the  borders,  making  sand-flats,  mud-flats, 
and  ultimately  good  dry  land,  to  widen  the  serviceable  area 
of  the  continent. 

The  banks  and  bottom  of  a  river  are  generally  made  of  coarser 
or  finer  material,  according  to  its  rate  of  flow  in  the  different 
parts.  Where  it  is  very  slow  the  bottom  and  banks  are  sure 
to  be  of  mud,  for  the  very  slow  movement  of  the  waters  gives 
a  chance  for  the  finest  detritus  to  settle;  but  if  rapid  it  will 
consist  of  pebbles,  if  the  region  contains  them.  The  bank 
struck  by  the  current  is,  in  general,  more  pebbly  than  the 
opposite. 

The  action  of  the  waters  of  large  lakes  in  rock-making  is 
to  a  great  degree  the  same  as  that  of  the  ocean. 

5.   The  Work  of  the  Ocean. 

The  mechanical  work  of  the  ocean  has  been  carried  forward 
chiefly  through  (1)  its  tidal  movements ;  (2)  its  waves ;  and 
(3)  its  currents. 

1.  Tides.  —  With  each  incoming  tide  the  waters  flow  up  the 
coast  and  into  all  bays  and  mouths  of  rivers,  rising  several 
feet  and  sometimes  yards  above  low-tide  level;  and  then,  with 
the  ebb,  the  same  waters  flow  back  and  leave  once  more  the 
mud-flats  and  sand-banks  of  the  bays  and  coasts  exposed  to 
view.  This  retreat  of  the  tide  allows  the  rivers  to  discharge 
freely  and  carry  out  their  detritus  to  sea ;  but  soon  again  the 
inflow  stops  the  movement  outward  and  reverses  it,  and  dur- 


WORK  OE  THE  OCEAN.  51 

ing  the  time  of  slackened  flow  the  waters  drop  their  detritus, 
—  part  about  the  mouth  of  the  stream,  part  along  the  adjoin- 
ing coast,  and  part  in  the  shallow  waters  of  the  sea  outside. 

2.  Waves.  —  The  sea  in  its  quiet  state  is  rarely  without 
some  swell,  which  causes  at  short  intervals  a  gentle  movement 
on  the  beach  and  some  rustling  of  the  waters  along  rocky 
shores.  Generally  there  are  waves  and  breakers;  and  when  a 
heavy  storm  is  in  progress  the  waves  rise  to  a  great  height 
and  plunge  violently  upon  the  beach  and  against  all  exposed 
cliffs,  wave  following  wave  in  quick  succession  through  days 
or  it  may  be  weeks  together.  With  each  storm  the  waves 
renew  their  violent  strokes,  and  in  many  seas  the  action  is 
incessant. 

*  The  plunge  on  the  beach  grinds  the  stones  against  one  an- 
other, rounding  them  and  finally  reducing  them  to  sand,  and 
the  sand  to  finer  sand.  The  waters  after  the  plunge  retreat 
down  the  beach  underneath  the  new  incoming  wave;  and  this 
"  undertow "  carries  off  the  finer  sand  made  by  the  grinding 
to  drop  it  in  the  deeper  waters  off  the  coast,  leaving  the 
coarser  to  constitute  the  beach. 

Thus  wave-action  grinds  to  powder  and  removes  the  feldspar 
and  other  softer  minerals  of  the  sand,  and  leaves  behind  the 
harder  quartz  grains;  and  consequently,  wherever  there  are 
beaches  of  sand,  there  are  offshore  deposits  of  mud  made  out 
of  the  fine  material  carried  seaward  by  the  undertow.  In  no 
age  of  the  world  have  sand-beds  been  formed  without  the 
making  of  mud-beds  somewhere  in  their  vicinity. 


52  MAKING  OE  ROCKS. 

The  cliffs,  or  exposed  ledges  of  rock,  are  worn  away  under 
the  incessant  battering,  and  afford  new  stones  and  sand  for 
the  beach,  and  the  shallow  waters  adjoining.  Most  rocky 
shores,  especially  those  of  stormy  seas,  show,  by  their  rugged 
cliffs,  needles,  arches,  and  rocky  islets  the  effects  of  the  storm- 
driven  waves. 

It  is  to  be  remembered  that  the  ocean,  as  stated  on  page 
42,  often  finds  the  work  of  destruction  facilitated  by  the 
weakening  or  decomposition  the  rocks  have  undergone  through 
the  quiet  action  of  air  and  moisture,  and  also  through  other 
means  explained  beyond  (page  63). 

The  waves,  as  they  move  toward  the  shores  over  the  shelv- 
ing bottom,  bear  the  sediment  in  the  waters  shoreward,  and 
throw  more  or  less  of  it  on  the  beach.  And  thus  the  beach 
grows  in  extent.  The  sediment  is,  in  general,  either  what  it 
gets  from  the  battered  rocks  of  the  coast,  or  what  the  rivers 
pour  into  the  sea.  At  the  present  time  the  Atlantic  receives 
an  immense  amount  of  detritus  through  the  many  large  streams 
of  Eastern  North  America;  and  as  a  consequence  the  shores 
aa-e  extensive  sand-flats  from  New  York  southward,  with  shal- 
low sounds  inside ;  and  the  latter  are  the  spaces  not  yet  filled 
to  the  water-level  with  the  deposits  of  detritus.  The  coast 
has  been  growing  seaward  for  ages  through  the  same  means, 
with  but  little  aid  from  the  wear  of  sea-shore  cliffs.  But  in 
the  earlier  geological  ages  this  was  not  so;  for  the  continent 
was  to  a  large  extent  more  or  less  submerged,  and  the  waves 


WORK  OP  THE  OCEAN.  53 

made  a  free  sweep  over  its  surface,  battering  the  rocks  in  many 
places,  and  thus  making  its  own  sediment;  for  there  were  only 
small  streams  on  the  small  lands  to  give  any  help. 

In  the  warmer  seas  of  the  world  mollusks  are  very  abundant. 
The  heavier  storm-waves  tear  them  from  the  muddy  bottom 
where  they  were  alive,  and  throw  them  on  the  beach.  There 
they  are  exposed  to  the  incessant  grinding  which  stones  and 
ordinary  sands  experience  elsewhere,  and  thus  are  reduced  to 
sand.  Every  storm  adds  to  the  shells  of  the  beach  as  well 
as  to  the  shell-sand.  Thus  sand-deposits  form  that  are  made 
out  of  shells  alone;  and  they  keep  growing  and  may  become 
of  great  extent.  The  finer  shell-sand  is  swept  out  into  the 
shallow  waters,  and  there  produces  a  finer  deposit.  The  hard- 
ening of  such  deposits  makes  limestone ;  and  the  shells  that 
happen  to  escape  the  grinding  are  its  fossils.  In  this  way 
limestones  have  been  made  in  all  geological  ages.  Shell  rocks 
are  now  forming  at  St.  Augustine,  Florida,  and  the  limestone 
there  made  is  used  as  a  building-stone. 

In  other  parts  of  tropical  seas  there  are  corals  growing 
profusely  within  reach  of  the  waves,  or  within  100  feet  of 
the  surface.  Many  are  broken  or  torn  up  by  the  waves  and 
carried  to  the  beach,  and  there  are  ground  up  and  spread  out 
in  beach  deposits  and  off-shore  deposits.  These  beds  of  coral 
sand  or  mud  harden,  and  then  become  the  coral  reef  rock, 
- — a  true  limestone,  similar  to  many  of  ancient  time.  South 
of  Florida,  and  in  other  parts  of  the  West  Indies,  in  various 


54  MAKING  OF  ROCKS. 

parts  of  the  tropical  Pacific,  and  also  in  the  East  Indies  and 
Red  Sea,  these  coral  limestones  are  now  in  progress. 

3.  Currents,  —  The  ocean  has  its  system  of  circulation,  or 
of  great  currents.  The  Gulf  Stream  is  part  of  it;  its  waters, 
flowing  westwardly  in  the  tropical  Atlantic,  bend  northward 
as  they  pass  the  West  India  seas,  and  then  pass  northeast- 
ward, parallel  with  the  North  American  coast  as  far  as  New- 
foundland, gradually  curving  eastward.  Thence  a  part  continues 
either  side  of  Iceland  to  the  Arctic  seas,  from  which  there  is 
a  return,  as  a  cold  Labrador  current,  along  the  coast  of  Lab- 
rador and  farther  south.  This  great  current  moves  but  5 
miles  an  hour  when  swiftest,  and  this  only  in  part  of  the 
straits  of  Florida.  Its  average  rate,  parallel  with  North  Amer- 
ica, is  2i  miles  an  hour;  and  it  is  hardly  felt  at  all  anywhere 
along  the  sides  of  the  continent,  not  even  in  the  Florida 
straits.  It  hence  gets  no  detritus  from  the  wear  of  coasts, 
and  is  too  feeble  to  carry  anything  but  the  very  finest  silt. 
The  ocean's  bottom  shows  that  it  receives  almost  nothing 
either  in  this  way  or  from  the  currents  of  great  rivers.  When, 
however,  the  continents  were  submerged  a  few  hundred  feet 
or  less  in  ancient  time,  the  currents  swept  over  the  surface, 
and  must  have  done  much  work  in  wearing  rocks  and  trans- 
porting detritus. 

Both  waves  and  gentle  currents  raise  ripples  over  the  sands; 
and  such  ripple-marks,  made  by  the  ocean  in  ancient  times, 
are  often  preserved  in  the  rocks  (Fig.  49).  They  show  that 


WORK   OF  THE  OCEAN. 


55 


the  sands  of  which  the  rocks  were  there  formed  were  within 
reach  of  waves  or  gentle  currents. 

The  mud  of  a  mud-flat  or  of  a  dried-up  puddle  along  a 
roadside  is  often  found  cracked  as  a  consequence  of  drying; 
and  such  mud-cracks  are  frequently  preserved  in  sedimentary 
rocks  (Fig.  50).  They  are  of  great  interest  to  the  geologist; 
for  they  show  that  the  layer  in  which  they  occur  was  not  of 


Figs.  49,  50. 


49 


Ripple-marks.  Mud-cracks. 

deep- water  origin;  but  beyond  question  was  exposed,  for  a 
while  at  least,  above  the  water's  surface  to  the  drying  air  or 
sun,  as  mud  is  now  often  exposed  along  a  roadside,  or  over 
the  mud-flats  of  an  estuary.  Such  cracks  become  filled  with 
the  next  deposit  of  detritus,  and  this  filling  has  often  been 
afterward  so  consolidated  as  to  be  harder  than  the  rock  out- 
side; and  hence  on  a  worn  surface  the  fillings  of  the  cracks 


56 


MAKING  OF  ROCKS. 


Fig.  51. 


Rain-drop  impressions. 


generally   make  a  network  of  little   ridgelets,  as   in  the   pre- 
ceding figure. 

Again,  mud-flats  sometimes  have  the  surface  covered  with 
rain-drop  impressions  after  a  short  shower  in  which  the  drops 
were  large;  and  many  shales  (rocks  made  of  mud  or  clay) 

retain  these  markings  (Fig. 
51)  ;  others  have  impressions 
of  the  footprints  of  animals, 
even  those  of  insects. 

Such  delicate  impressions 
are  preserved,  because  soon 
after  they  are  made  they  be- 
come covered  with  a  layer 
of  fine  detritus;  and  after  that  nothing  can  erase  them  short 
of  the  removal  of  the  deposit  itself. 

The  rocks  that  have  been  made  by  fresh  waters  and  the 
oceans  are  of  vast  extent.  They  are  the  sandstones,  conglom- 
erates, and  shales  of  the  world;  and  they  include  the  limestones 
also.  The  ocean  has  done  far  the  larger  part  of  the  rock-mak- 
ing. In  the  earlier  geological  ages  it  worked  almost  alone;  for 
the  lands  were  very  small,  and  only  large  lands  can  have  large 
rivers  and  river  deposits.  Afterward,  in  the  coal-era,  there 
was  at  least  one  large  delta  or  estuary  on  the  borders  of  the 
American  continent, — that  of  the  St.  Lawrence;  and  ever  since 
rivers  have  given  important  aid.  During  the  last  of  the  ages, 
after  the  continents  had  reached  nearly  their  present  extent, 


WORK  OF  ICE.  57 

and  the  mountains  their  modern  height  and  numbers,  rivers 
have  done  the  larger  part  of  the  distribution  of  rock-material. 
Sedimentary  rocks  show  that  they  were  formed  through  the 
action  of  water,  often  in  the  rounded  or  water-worn  pebbles 
they  contain,  or  the  water-worn  sand,  or  from  a  resemblance 
in  constitution  to  a  consolidated  bed  of  mud  or  clay;  in  their 
relics  of  aquatic  life,  and  the  indications  of  wave-action  or  cur- 
rent-action above  pointed  out;  and  in  their  division  into  layers, 
such  as  exist  in  known  sediments  or  deposits  from  waters. 

6.    The  Work  of  Ice. 

1.  Expansion  on  freezing.  —  When  water  freezes  it  expands. 
If  it  freeze  in  a  pitcher,  the  expansion  is  pretty  sure  to  break 
the  pitcher.     If  it  freeze  in  the  crevice  of  a  rock,  it  opens  the 
crevice;  and  by  repeating  the  process  winter  after  winter  in  the 
colder  countries  of  the  globe,  it  pries  off  and  breaks  apart  rocks, 
and  makes  often  a  slope  of  broken  blocks,  or  talus,  at  the  foot 
of  a  bluff.     By  opening  cracks  in  this  wray  it  gives  air  and 
moisture  new  chances  to  do  their  quiet  work  of  destruction. 

2.  Transportation   by   the   ice  of   rivers   or   lakes.  —  When 
water  freezes  over   a   river  it   often  envelops  stones  along  the 
shore ;  and  then,  whenever  there  is  a  breaking  up,  the  ice  with 
its  load  of  stones  is  often  floated  off  down  stream;  or  if  the 
water  of  a  stream  or  lake  rises  in  consequence  of  a  flood,  the 
stones  may  be  carried  farther  up  the  shore  and  dropped  there. 

In  cold  countries  ice  often  forms  thickly  about  the  stones 

3* 


58  MAKING  OF  ROCKS. 


in  the  bottom  of  a  stream;  and  as  it  is  lighter  than  water  it 
may  become  thick  enough  to  serve  as  a  float  to  lift  the  stone 
from  the  bottom,  so  that  both  ice  and  stone  journey  together 
with  the  current. 

These  are  commonplace  ways  in  which  ice  does  geological 
work.  Its  greater  labors  are  performed  when  it  is  in  the 
condition  of  a  glacier. 

3.  Glaciers.  —  Glaciers  are  broad  and  deep  streams  of  ice 
in  the  great  valleys  of  snowy  mountains  like  the  Alps.  The 
snows  that  fall  about  the  summits  above  the  level  of  perpetual 
snow  accumulate  over  the  high  region  until  the  depth  is  one 
or  more  hundred  feet.  At  bottom  it  is  packed  by  the  press- 
ure and  becomes  ice.  Its  weight  causes  the  ice  to  descend 
the  slopes  of  the  mountains  and  along  the  valleys,  which  it 
fills  from  side  to  side.  The  width  of  the  ice  of  the  valley 
may  be  several  miles;  its  depth  in  the  Alpine  valleys  is  gen- 
erally from  200  to  500  feet.  ' 

The  glaciers  descend  far  below  the  line  of  freezing  to  where 
the  fields  are  green  and  gardens  flourish;  and  this  takes  place 
because  there  is  so  thick  a  mass  of  ice.  In  the  Alps  the 
glaciers  stretch  down  the  valleys  4,500  to  5,300  feet  below 
the  snow-line.  At  Grindelwald  two  glaciers  terminate  within 
a  short  distance  of  the  village. 

The  rate  of  movement  in  the  Alps  in  summer  is  mostly 
between  10  and  20  inches  a  day,  and  half  this  in  winter;  12 
inches  a  day  corresponds  to  a  mile  in  about  14i  years. 


WORK  OF  ICE. 


59 


Fig.  52  (from  a  sketch  in  one  of  Agassiz's  works  on  glaciers) 
represents  one  of  these  great  ice-streams  or  glaciers  descending 
a  valley  in  the  Monta  E/osa  region  of  the  Alps.  A  valley  often 
narrows  and  widens  at  intervals,  and  changes  its  slope  at  times 

Fig.  52. 


Glacier  of  Zermatt,  or  the  Corner  Glacier. 


from  a  precipitous  to  a  horizontal  surface.  The  ice  has  to  ac- 
commodate itself  to  all  these  variations.  On  turning  an  angle 
it  is  broken,  or  has  great  numbers  of  deep  <f  crevasses  "  made 
through  it,  especially  on  the  side  opposite  the  angle.  On  com- 


60 


MAKING  OF  ROCKS. 


mencing  a  rapid  descent,  great  breaks,  or  crevasses,  cross  the 
glacier  from  one  side  to  the  other.  On  reaching  a  level  place 
again  the  ice  closes  up,  and  the  glacier  loses  nearly  all  its 
crevasses.  The  ice  is  brittle,  and  freezes  together  when  the 
separated  parts  are  brought  in  contact  again;  so  that,  as  it 
moves,  it  goes  on  breaking  and  mending  itself.  Ice  is  plastic ; 
for  it  may  be  made  into  rods  by  pressing  it  through  a  hole, 
and  will  take  the  impress  of  a  medal ;  so  that  it  can  accommo- 
date itself  in  this  way  also  to  the  changing  character  of  the 
surface  over  which  it  moves. 

Along  the  sides  of  the  glacier  the  cliffs  of  rock  often  send 
down  stones  and  earth,  or  avalanches  of  ice  and  rocks;  and 
these  make  a  line  of  earth  and  rocks  along  either  margin,  which 

Fig.  53. 


Glacial  scratches  and  planing. 

is  called  a  moraine.  These  moraines  are  carried  with  the  ice 
to  where  it  melts,  and  there  dropped.  Other  blocks  are  taken 
up  by  the  sides  and  bottom  of  the  glacier. 


WORK  or  ICE. 


61 


Wherever  a  glacier  has  moved  the  rocks  are  scratched, 
planed,  or  polished,  often  with  great  perfection,  as  illustrated 
in  Fig.  53. 


Fijr.  54. 


View  on  Roche-Moutonn^e  Creek,  Colorado. 

Ledges  of  rocks  also  are  rounded,  making  what  are  called 
sheep-backs,  or,  in  French,  roches  moutonnees.  Fig.  54  repre- 
sents the  roches  moutonnees  in  a  valley  of  the  mountains  of 
Colorado,  —  a  valley  leading  up  to  the  Mountain  of  the  Holy 
Cross,  seen  in  the  distant  part  of  the  view.  It  is  from  the 
Beport  of  Dr.  Hay  den  for  1873.  No  glaciers  exist  there 
now;  but  once  they  were  of  great  extent  and  depth.  The 


62  MAKING  OF  ROCKS. 

scratching  and  polishing  are  done  by  the  stones  in  the  bottom 
and  sides  of  the  glacier;  and  these  stones,  as  is  natural,  are 
also  planed  off  and  scratched. 

4,  Icebergs,  —  In  the  Arctic  regions  the  glaciers  of  Green- 
land, loaded  with  their  moraines,  extend  down  into  the  sea, 
and  the  part  in  the  water  sooner  or  later  breaks  off  and  floats 
away  as  an  iceberg.  These  icebergs  are  carried  south  by  the 
Labrador  current,  and  large  numbers  of  them  in  the  course  of 
a  season  reach  the  Banks  of  Newfoundland.  There*  they  find 
the  waters  warmer,  in  consequence  of  the  nearness  of  the  Gulf 
Stream,  and  they  melt  and  drop  their  burden  of  stones  and 
earth  into  the  waters.  It  has  been  suggested  that  the  Banks 
of  Newfoundland  owe  their  existence  to  the  melting  and  con- 
sequent unlading  there  of  icebergs. 

It  thus  appears  that  ice  does  geological  work  (1),  in  the  act 
of  formation,  through  its  expansion ;  as  glaciers,  (2)  by  trans- 
porting over  the  land  earth  and  stones  and  rocks, — some  of  the 
rocks  as  large  as  ordinary-sized  houses,  —  and  dropping  them 
when  the  ice  melts;  (3)  by  tearing  apart  rocks  through  its 
movement  wherever  there  are  opened  seams  into  which  it  can 
pass ;  (4)  by  wearing  deeply  into  the  soft  rocks  over  which  it 
may  move,  and  scratching  and  polishing  hard  rocks;  and,  as 
floating  ice  or  icebergs,  by  transporting  rocks,  stones,  and  earth 
from  one  region  to  another;  and  (5)  it  often  makes  temporary 
dams  across  valleys,  that  cause  great  devastation  when  they 
give  way. 


WORK  OF  HEAT.  63 


7.    The  Work  of  Heat  in   Rock-making. 

The  effects  here  mentioned  are  the  following :  — 

1.  Expansion  and  contraction  from  change  of  temperature. 

2.  The  fusion  of  rocks,  and  their  ejection  through  volcanic 
vents  and  fissures. 

3.  Solidification    and    crystallization    of    fragmental    rocks, 
through  long-continued  heat,  and  the   filling  of  fissures  and 
making  of  veins. 

1.    Through  Expansion  and  Contraction. 

Owing  to  the  alternation  each  day  of  sunlight  and  darkness, 
the  surfaces  of  exposed  rocks  experience  an  alternate  heating 
and  cooling,  and  therefore  alternate  expansion  and  contraction. 
This  cause,  which  is  sufficient  to  break  the  solder  of  soldered 
metallic  roofs  on  houses,  to  loosen  the  cemented  blocks  of  a 
stone  wall,  and  to  give  a  perceptible  movement  to  high  stone 
towers,  tends  to  start  off  the  grains,  and  sometimes  separates 
an  outer  layer  from  bare  rocks,  especially  when  the  surface  is 
weathered.  As  it  is  in  action  over  the  whole  surface  of  the 
earth,  it  is  an  important  addition,  in  a  quiet  way,  to  the 
chemical  work  of  air  and  moisture,  in  the  making  of  earth  or 
gravel  for  the  formation  of  rock  deposits;  and  it  has  been  so 
ever  since  the  sun  first  shone  upon  bare  rocks.  A  foot  or  two 
of  soil  is  a  protection  against  this  method  of  degradation. 

Heat   gaining    access   to   rocks   beneath    a    region    expands 


MAKING  OF  ROCKS. 


them  and  causes  an  elevation  of  the  surface;  and  loss  of  heat 
produces  a  reverse  effect.  Fractures  may  attend  such  changes 
of  level,  and  also  light  earthquakes. 

2.    Making  of  Rocks  through  Fusion:  Volcanoes. 
L  Volcanoes.  —  Igneous  rocks,  or  those  made  by  the  cooling 
of  melted  rock-material,  are   described  on  page  18  as  having 

Fig.  65. 


Mount  Shasta,  from  the  north  :  from  a  photograph  by  Watklns. 

come  to  the  earth's  surface  from  below  through  fissures  5  and 
also  as  sometimes  having  been  ejected  at  intervals  from  one 
and  the  same  opening  for  long  periods  of  time. 


WORK  OF  HEAT.  65 


When  fissures  are  filled  and  closed  by  one  eruption,  they 
make  dikes  of  igneous  rock,  and  also  one  or  more  beds  if 
the  melted  material  flows  from  the  fissure  over  the  region 
adjoining. 

But  when  a  vent  remains  open  for  many  successive  eruptions 
it  becomes  then  the  centre  of  a  true  volcano  or  fire-mountain. 
The  outflows  of  liquid  rock,  and  ejections  of  volcanic  sand  or 
cinders  from  one  side  and  the  other  around  the  vent,  produce 
a  hill  or  mountain  of  a  form  more  or  less  nearly  conical. 
Fig.  55  represents  Mount  Shasta,  one  of  the  volcanic  mountains 
of  Western  North  America,  having  an  elevation,  according  to 
Whitney,  of  14,440  feet.  It  is  not  now  in  action,  yet  has 
hot  springs  near  its  summit.  It  also  represents  well  the  gen- 
eral form  of  the  great  volcanoes  of  the  Cascade  range  to  the 
north  of  it  in  Oregon,  and  of  those  along  the  Andes  in  South 
America.  Of  the  latter  Cotopaxi  is  an  active  volcano  19,660 
feet  in  height,  and  Arequipa  another,  18,877  feet,  while  Acon- 
cagua, of  Chili,  has  a  height  of  22,478  feet,  and  is  the  loftiest 
peak  in  the  Andes. 

Active  volcanoes  send  forth  only  vapors  in  their  times  of 
quiet.  In  periods  of  eruption  streams  of  lava  (or  liquid  rock) 
are  poured  out,  —  either  over  the  edge  of  the  crater  or 
through  breaks  in  the  sides  of  the  mountain.  The  latter  is 
the  common  mode.  At  the  same  time  cinders  —  or  fragments 
of  lava  —  are  often  thrown  from  the  crater  to  a  great  height 
above  the  volcano,  to  fall  in  showers  around. 


66  MAKING  OF  ROCKS. 

Volcanoes   vary   much  in   angle   of  slope.     When  made  of 
cinders  the  angle  is  often  40°  to  42°.     If  formed  through  the 
alternations  of  lavas  and  cinders,  or  of  tufas,  the  slope  may  be 
30°  or  less,  as  in  Figs.  55  and  56.    Fig.  56  gives  the  slopes  of 
rig.  56.  the  volcano  of  Jorullo,  in  Mexico.    Many 

of  the  grandest  volcanoes  of  the  world, 
^^  like  Etna,  and  those  of  Hawaii,  in  the 
Sandwich  Islands,  have  an  exceedingly  gentle  slope,  —  the 
height  only  a  twentieth  of  the  breadth,  as  in  Fig.  57,  giving 
the  slope  of  Mount  Loa,  of  Hawaii.  These  last  are  made 
almost  solely  of  lavas;  and  they  have  so  gentle  a  slope,  be- 
cause the  melted  rock  of  the  region  flows  off  freely. 

The  eruptions  of  volcanoes  are  owing  mainly  to  the  waters 
that  gain  access  to  the  fires.     The  rains  of  the  region  produce 

Fig.  57. 


underground  streams  that  descend  and  pass  into  the  melted 
rock,  there  to  be  changed  to  vapor ;  and  sea- water,  when  vol- 
canoes are  near  or  in  the  ocean,  presses  its  way  in,  or  gains 
access  suddenly  through  fractures.  The  vapor  penetrating  the 
liquid  mass  expands  the  whole,  causing  it  to  rise  in  the  vent. 
The  fires  become  hotter  with  the  increasing  height  of  the  col- 
umn of  melted  rock  in  the  mountain,  and  the  vapors  more 
active.  The  pressure  from  the  high  liquid  column,  and  from 
the  vapors,  breaks  the  mountain,  and  the  lavas  run  out,  devas- 


WORK  OP  HEAT.  67 


tating  the  country,  it  may  be,  for  a  score  of  miles  or  more. 
When  the  sea  gains  sudden  access  to  a  volcanic  vent,  the  erup- 
tion is  accompanied  with  violent  quakings  of  the  mountain. 
Every  few  years  the  country  on  one  side  or  another  of  Yesuvius 
is  deluged  with  the  fiery  rock,  cultivated  fields  buried,  and  not 
unfrequently  villages  destroyed.  Pompeii  and  Herculaneum 
were  buried  beneath  the  cinders  of  an  eruption  that  took  place 
in  the  year  79  of  our  era;  and  since  then  several  streams  of 
lava  have  flowed  down  over  Herculaneum,  adding  to  the  depth 
of  rock  over  it.  The  deposits  of  cinders  make  a  kind  of  soft 
sandstone  called  tufa. 

Mount  Loa,  on  Hawaii,  has  had  six  great  eruptions  througli 
fissures  in  the  sides  of  the  mountain  within  30  years.  There 
is  a  summit  crater  (L  on  the  map)  at  a  height  of  13,760  feet, 
and  another  called  Kilauea  (at  P),  nearly  4,000  feet  above  the 
sea,  which  is  the  larger  of  the  two.  The  map  shows  at  1,  2, 
3,  4,  5,  and  between  P  and  K,  the  courses  of  the  eruptions. 
K  is  the  position  of  another  volcanic  mountain,  Mount  Kea, 
as  high  as  Loa,  and  H,  of  another,  10,000  feet  high. 

The  liquid  rock  comes  up  from  some  deep-seated  fire-region. 

Yolcanic  mountains  are  very  numerous  along  the  Andes; 
in  Central  America  and  Mexico;  in  Oregon  and  Washington 
Territory,  from  Mount  Shasta  to  Mount  Baker  and  beyond;  in 
the  Alaska  archipelago  on  the  north;  all  along  the  west  side 
of  the  Pacific  through  Japan  and  the  East  Indies ;  southward 
in  the  New  Hebrides,  New  Zealand,  and  in  Antarctic  regions. 


68 


MAKING  OF  ROCKS. 


Thus  the  Pacific,  the  great  ocean  of  the  globe,  is  girt  with 
volcanoes,  besides  having  many  over  its  surface.  The  Atlantic, 
in  contrast  with  it,  has  none  on  its  borders,  except  in  the  Gulf 

Fig.  58. 


Island  of  Hawaii. 

L,  Mount  Loa  ;  K,  Mount  Kea  ;  H,  Mount  Hualalai ;  P,  Kilauea  or  Lua-Pdle"  ;  i,  Eruption  of  1843  ;  2.  of 
1852  :  3,  of  1855  ;  4,  of  1859  ;  a,  Waimea  ;  b,  Kawaihae  ;  c,  Wainanalii  ;  d,  Kailua  ;  e,  Kealakekua  ;  f, 
Kaulanamauna  ;  g,  Kailiki  ;  h,  Waiohinu  ;  i,  Honuapo  ;  J,  Kapoho  ;  k,  Nanawale  ;  /,  Waipio  ;  m,  first 
appearance  of  eruption  of  1868  ;  n,  Kahuku.  The  courses  of  the  currents  i,  2,  3,  and  5  are  from  a  map  by 
T.  Coan,  and  4,  from  one  by  A.  F.  Judd. 

of  Guinea  on  the  coast  of  Africa,  and  in  the  West   Indies; 
and  but  few  over  its  interior. 

Hot  springs  often  make  deposits  of  silica  around  them, 
owing  to  the  silica  the  heat  has  enabled  the  waters  to  take 
up  from  the  rocks  with  which  they  are  in  contact.  Such 


WORK  OF  HEAT. 


69 


Fig.  59. 


Beehive  Geyser  in  action. 

springs    sometimes   throw  their  waters   in   jets    at    longer  or 


70  MAKING  OF  ROCKS. 

shorter  intervals,,  and  they  are  then  called  geysers.  One  of 
the  geysers  of  the  Yellowstone  Park,  in  the  Rocky  Mountains 
(where  there  are  great  numbers  of  them),  is  represented  in  ac- 
tion in  Pig.  59,  taken  from  Hayden's  Report  for  1873.  It 
throws  the  water  to  a  height  of  200  feet  or  more.  The  gey- 
sers of  Yellowstone  Park  are  mostly  about  the  Pire-hole  River, 
a  fork  of  Madison  River,  and  near  Shoshone  Lake,  the  head  of 
Snake  River,  and  not  far  from  the  head  of  the  Yellowstone. 
The  number  of  hot  springs,  hot  lakes,  and  geysers  in  the  Park 
has  been  stated  to  be  not  less  than  10,000. 

Solfataras  are  regions  about  volcanoes  where  vapors  issue 
and  sulphur  is  deposited.  The  name  is  from  the  Italian  for 
sulphur. 

3.    Solidification,  Metamorphism,  and  Formation  of  Veins. 

1.  Solidification.  —  Limestones  have  been  solidified  through 
carbonate  of  lime  (bicarbonate)  in  solution  in  waters;  also 
some  sandstones  by  the  same  means,  the  lime-salt  being  de- 
rived from  the  grains  of  shells,  corals,  etc.,  in  these  rocks. 
Some  sandstones  have  been  partially  hardened  by  the  silica  in 
solution  in  many  cold  waters,  especially  where  there  are  diatoms 
(page  35)  in  the  rock,  to  enter  into  solution.  The  masses  of  flint 
and  hornstone  in  rocks  are  made  out  of  diatoms  and  other  sili- 
ceous relics  (page  38)  by  consolidation  in  cold  waters;  and  many 
fossils  have  been  turned  to  quartz  (silica)  in  the  same  way. 

But  some  of  the  oldest  of  sandstones  and  shales  are  still 


WORK  OF  HEAT.  71 


soft  or  unconsolidated.  A  large  part  of  the  more  solid  have 
had  the  aid  of  heat  in  solidification,  —  heat  producing  siliceous 
waters  for  the  work.  Hot  waters  containing  in  solution  some 
alkali,  as  soda  or  potash,  have  the  power  of  dissolving  silica; 
and  they  find  both  the  silica  and  the  needed  alkali  in  the 
feldspar  of  igneous  or  other  rocks,  and  hence  the  waters  of 
hot  springs  are  generally  siliceous. 

2.  Metamorphism.  —  This  heat,  when  it  has  been  long  con- 
tinued, —  probably  for  thousands  of  years,  —  has  not  only  con- 
solidated the  rocks,  but  has  also  crystallized  them,  turning 
sandstones,  shales,  and  conglomerates  into  the  metamorphic 
rocks,  granite,  gneiss,  mica  schist,  hornblende  rock,  and 
other  kinds.  Those  fragmental  rocks  were  made  by  the  pul- 
verizing of  granite,  gneiss,  mica  schist,  and  the  related  rocks; 
and  hence  the  return  to  granite,  gneiss,  mica  schist,  and  the 
like  by  a  new  crystallization,  when  acted  upon  throughout  by 
heat  and  moisture,  is  not  a  matter  of  surprise. 

Moisture  at  a  high  temperature  has,  moreover,  great  decom- 
posing and  recomposing  power ;  and  many  minerals  —  as  mica, 
feldspar,  hornblende,  and  others  —  may  be  made  and  crystal- 
lized through  its  action,  and  thus  become  constituents  of  met- 
amorphic  deposits  when  not  originally  present.  The  heat  of 
metamorphism  was  generally  much  below  that  of  fusion,  this 
being  obvious  from  the  fact  that  the  stratification  of  the  rocks 
is  perfectly  retained;  for  the  layers  of  mica  schist  and  gneiss 
correspond  with  the  bedding  of  the  sandstone  or  shale  out  of 


72  MAKING  OF  ROCKS. 

which  they  were  made.  But,  in  some  cases,  the  heat  was  suffi- 
cient to  soften  the  rock,  and  then  the  planes  of  stratification 
were  obliterated,  making  granite  instead  of  gneiss,  —  granite 
differing  from  gneiss  only  in  the  absence  of  anything  like  strat- 
ification or  an  arrangement  of  the  material  in  layers.  There 
are  all  shades  of  gradation  between  granite  and  gneiss. 

Heat  has  changed  common  or  compact  limestones,  that 
were  gray  to  black  in  color  and  full  of  fossils,  into  white  or 
clouded  crystalline  limestones,  that  is,  white  or  clouded  mar- 
bles. In  a  case  of  this  kind  the  metamorphism  may  have  con- 
sisted simply  in  crystallization.  Yet  at  the-  same  time  the 
impurities  of  the  limestone  have  sometimes  been  converted  by 
the  process  into  grains  of  mica  and  other  minerals,  which  are 
distributed  through  the  rock.  Similarly  other  rocks,  like  mica 
schist,  gneiss,  etc.,  have  been  filled  with  various  crystallized 
minerals,  as  garnet,  tourmaline,  staurolite;  and  even  the  gems, 
sapphire,  ruby,  topaz,  and  the  diamond  are  among  the  results 
of  the  metamorphic  process.  Moreover,  beds  of  earthy  iron- 
ores  have  been  made  into  crystalline  iron-ores,  examples  of 
which  on  a  grand  scale  occur  in  the  Adirondack  region  of 
Northern  New  York,  the  Marquette  region  in  Michigan,  and 
in  the  Iron  Mountains  of  Missouri. 

Metamorphism  has  been  carried  on  at  once  over  regions 
thousands  of  square  miles  in  area.  The  rocks  undergoing  the 
change  were  undergoing  also  an  upturning  and  fracturing  on 
a  scale  as  extensive  j  and  the  movements  were  the  source  of 


WORK  OF  HEAT.  73 


the  heat  that  caused  the  metamorphism,  just  as  the  rubbing 
of  two  sticks  together  produces  heat.  The  upturned  ore-beds 
often  look  like  veins  of  ore,  and  are  sometimes  wrongly  so 
called. 

Hot  springs  occasionally  produce  metamorphism  in  the  rocks 
about  them,  besides  causing  ordinary  consolidation.  The 
waters  of  geysers  (page  68)  deposit  a  large  amount  of  silica 
ill  the  form  of  opal,  making  opal  basins  for  themselves  to 
play  in,  and  spreading  the  opal  widely  over  the  region  around. 
They  also  produce  the  petrifaction  of  wood,  changing  the  trunk 
of  a  tree  into  silica,  and  generally  without  obliterating  the 
grain  or  structure  of  the  wood.  But  the  making  of  such 
petrifactions  does  not  demand  heat,  as  they  have  often  been 
produced  in  beds  of  earthy  or  calcareous  mud  when  siliceous 
infusoria  were  abundant  in  it,  as  stated  on  page  70. 

The  opal  of  geyser  regions  is  of  a  coarse  kind,  yet  is  often 
beautiful  in  its  forms  about  the  pools.  The  precious  opal  has 
been  mostly  produced  in  feldspathic  lavas  (trachytes)  that  have 
been  long  subjected  to  hot  waters,  and  which,  under  the  ac- 
tion, have  yielded  up  part  of  their  silica  to  deposit  it  again 
as  opal  in  the  cavities  of  the  rock. 

3.  Veins,  —  Rocks  have  often  been  extensively  broken  so  as 
to  be  intersected  by  great  numbers  of  fissures  large  and  small; 
and  in  upturnings  the  layers,  especially  of  shaly  rocks,  have 
been  opened,  as  the  leaves  of  a  quire  of  paper  are  separated 
more  or  less  on  bending  it  into  an  arch.  The  fissures,  in 

4 


MAKING  OF  ROCKS. 


such  cases,  and  all  the  openings,  have  become  filled  while  met- 
amorphic  changes  were  in  progress,  by  crystallized  rock-mate- 
rial, derived  from  the  rock  either  side  of  the  fracture  or  from 
depths  below ;  and  metallic  ores  of  various  kinds,  as  of  lead, 
silver,  and  copper,  and  also  native  gold,  have  often  been  car- 
ried into  the  openings  or  fissures  along  with  the  rock-material. 
Veins  (Figs.  60,  61)  are  the  fillings  of  fissures,  and  this  is  the 
most  common  way  in  which  they  have  been  made.  The  mate- 


Figs.  60,  61 


Rocks  Intersected  by  veins,  a.  b. 


rial  is  carried  in,  from  the  rocks  on  either  side  or  below,  by  the 
moisture  present,  this,  at  the  high  temperature,  dissolving  it ; 
and  thus  laden  it  has  pressed  into  all  opened  spaces,  there 
to  deposit  it  as  long  as  there  was  open  space  to  be  filled. 
Such  veins,  and  the  seams  occupying  openings  between  layers, 
afford  a  large  part  of  the  metals  of  the  world,  iron  excluded. 
Gold  is  found  in  such  veins,  or  else  in  the  gravel  made  out 
of  gold-bearing  rocks  by  some  process  of  wear  or  destruction. 
Many  veins  consist  of  quartz  alone  (such  are  most  gold- 
bearing  veins) ;  others  of  coarse  granite,  and  of  various  other 


MAKING  OF  VEINS.  75 

kinds  of  rock-material.  They  are  frequently  banded,  that  is, 
are  made  up  of  layers  parallel  to  the  walls.  These  layers 
consist  of  different  kinds  of  minerals  and  ores :  there  may  be 
an  outer  layer  of  quartz;  next  one  of  ore;  then  another  of 
quartz,  or  of  calcite,  or  of  some  other  earthy  mineral;  then 
perhaps  another  of  ore.  Such  a  structure  is  proof  that  the 
vein  was  filled  by  deposition  against  the  walls,  one  layer  after 
another,  and  that  they  were  not  made  by  injection  of  liquid 
rock  from  below. 

Other  metallic  veins  have  been  made  in  connection  with 
igneous  ejections.  Fissures  have  opened  down  to  regions  of 
liquid  rock,  and  sometimes  ores  have  ascended  along  with  the 
liquid  rock;  but  often,  in  some  part  of  the  same  disturbed 
region,  other  fissures  have  opened  which  have  received  from 
below  only  vapors  or  solutions  of  mineral  matter  including  the 
ores.  The  waters  that  exist  as  subterranean  streams,  especially 
beneath  stratified  rocks,  have  frequently  made  their  way  into 
such  opened  fissures,  and  there  becoming  at  once  highly 
heated,  have  aided  in  carrying  the  material  upward,  and  also 
in  determining  its  condition  and  its  arrangement  in  the  veins. 

In  Fig.  61  the  vein  a  is  broken  off  and  displaced — that 
is,  faulted  —  along  the  line  of  the  vein  6.  When  the  fissure 
occupied  by  the  vein  b  was  opened  the  rock  of  one  side 
slipped  by,  or  was  shoved  by,  that  of  the  other  side,  and  so 
the  fault  or  displacement  was  made.  Such  faults  are  very 
common. 


76  MAKING  OF  VALLEYS. 


II. —  Making  of  Valleys. 

VALLEYS  are  made  (1)  by  erosion  by  the  streams  of  the 
land,  —  the  common  way ;  (2)  by  uptif tings  or  flexures  of 
rocks  making  mountains  and  leaving  troughs  or  low  regions 
between  the  mountains  as  valleys ;  (3)  through  fractures  of 
the  earth's  crust. 

L  Valleys  of  erosion.  —  Slopes  of  sand  or  gravel  are  some- 
times deeply  gullied  by  the  heavy  rains  of  a  single  day,  or, 
in  geological  language,  deeply  eroded,  or  eaten  out  as  this 
word  means.  This  work  of  the  rains  often  gives  a  very  exact 
model,  on  a  small  scale,  of  the  valleys  and  ridges  of  moun- 
tain regions.  The  gully,  or  little  valley,  has  often  (1)  a  preci- 
pice at  its  head;  (2)  little  waterfalls  along  the  steep  part  of 
its  course,  wherever  there  was  a  harder  layer  of  sand;  (3)  a 
narrow  bottom  with  steeply  sloped  sides;  but,  near  the  foot 
of  the  hill,  where  the  surface  is  nearly  horizontal,  a  broad  and 
flat  bottom  of  sand  laid  down  by  the  spreading  waters.  And 
the  ridgelets  between  the  little  valleys  have  often  a  broken, 
knife-edge  summit  in  their  upper  part,  and  are  broader  below. 
The  reader  should  study  carefully  the  first  gullied  slope  of 
this  kind  that  he  may  meet  with,  for  it  will  be  a  study  of 
valley-making  over  the  world.  Only  a  single  night's  rain  may 
have  sufficed  to  make  the  little  valleys  and  ridgelets  of  the 
sand  slope,  because  the  sand  was  not  firmly  consolidated.  But 


MAKING  OF  VALLEYS.  77 

if  the  rocks  be  ever  so  hard  they  yield  in  the  same  way,  and 
with  time  enough,  the  same  forms,  on  the  scale  of  the  grand- 
est mountain  region  of  the  world,  have  resulted.  Many  of 
the  river-valleys  of  North  America,  and  of  other  continents, 
illustrate  this  action  of  running  water.  Watkin's  Glen,  near 
Ithaca,  Trenton  and  Niagara  Falls,  in  Central  and  Western 
New  York,  and  the  Valley  of  the  Upper  Mississippi,  afford 
examples. 

The  character  of  the  valleys  and  ridges  will  depend  much 
on  the  hardness,  structure,  and  position  of  the  rocks.  "When 
the  beds  are  nearly  horizontal,  precipices  and  waterfalls  are 
most  common. 

The  Colorado  Eiver  of  Western  North  America  runs  for  two 
hundred  miles  through  a  gorge  or  caiion  with  vertical  walls  of 
rock  in  many  places  over  3,000  feet  high.  The  sketch  in  Fig. 
62,  from  a  photograph  obtained  by  Powell's  expedition,  is  a  view 
of  a  portion  of  this  canon  between  the  Paria  and  the  mouth 
of  Little  Colorado,  called  Marble  caiion.  The  walls  in  the  dis- 
tant part  of  the  view  have  a  height  of  3,500  feet,  and  consist 
of  limestone,  whence  its  name.  But  in  other  parts  of  the  Col- 
orado canon  there  are  various  kinds  of  strata,  and  in  some 
places  the  cut  has  been  made  deep  into  the  underlying  granite, 
—  and  all  is  the  work  of  the  river.  The  waters  have  a  rapid 
and  often  plunging  flow,  owing  to  the  slope,  and  carry  along 
pebbles  and  stones,  and  these  stones  aid  greatly  in  the  erosion. 
But  to  wear  out  so  wide  and  deep  a  channel  a  long  period  of 


78 


MAKING  OE  VALLEYS. 


Fig.  62. 


Marble  Canon,  on  the  Colorado. 


time  was  required.  Above  the  gorge,  some  miles  back  from  the 
river,  the  horizontal  rocks  are  piled  up  to  a  still  greater  height, 
reaching  in  some  places  a  level  8,500  feet  above  that  of  the 
bed  of  the  stream ;  and  these  piles  of  strata  standing  in  sep- 
arate ridges,  sometimes  in  the  form  of  pinnacles,  castellated 
structures,  and  table-topped  mountains,  are  parts  of  great  rock- 
formations  that  once  spread  across  the  wide  region.  They 
show  that  erosion  has  carried  away  the  larger  portion  of  these 
upper  rocks,  the  mountains  and  pinnacles  being  merely  rem- 
nants of  them. 


MAKING  OF  VALLEYS.  79 

The  ocean  may  have  aided  in  the  removal  when  the  land 
stood  at  a  lower  level,  partly  submerged;  but  it  could  not 
have  cut  out  the  gorge  or  canon ;  for  the  work  of  the  ocean 
is  to  wear  off  headlands,  form  sand-flats  or  beaches  along 
coasts,  and  fill  up  bays,  not  to  cut  channels  into  a  coast 
and  make  deep  valleys.  The  ocean  has  done  but  little  valley- 
making,  and  only  that  of  the  broadest  kind,  when  its  wide 
currents  swept  over  the  submerged  continent.  The  gorging  of 
mountains  and  plains  it  has  left  to  the  running  waters  of  the 
land.  These  running  waters  have  been  aided  in  some  cases 
by  glacier-ice  (page  58). 

2.  Valleys  made  by  the  upheaval  of  mountains.  —  The  wide 
Mississippi  valley  is  a  depression  between  the  Eocky  Moun- 
tains on  the  west  and  the  Appalachians  on  the  east.  The 
making  of  these  mountains  was  the  making  of  the  valley. 
The  Connecticut  and  Hudson  Eivers  occupy  depressions  that 
were  probably  made  by  uplifts  either  side  of  them.  The  Adi- 
rondacks  are  among  the  oldest  of  mountains.  Long  after 
these  the  Green  Mountains  were  made;  and  when  raised,  the 
valley  in  which  lies  Lake  Champlain  ,was  a  region  left  low  at 
the  time.  Again,  the  valley  of  the  Sacramento  originated  in 
the  making  of  the  Sierra  Nevada  on  one  side,  and,  later,  the 
Coast  ranges  on  the  other..  The  other  continents  afford  simi- 
lar examples. 

8.  Valleys  made  by  fractures  of  the  earth's  crust  —  1.  A 
great  fissure  in  a  volcanic  mountain  opened  for  the  ejection 


80  MAKING  OF  MOUNTAINS, 

of  lavas  has  sometimes  been  left,  after  the  eruption  ceased,  as 
a  deep  valley.  2.  Great  regions  have  subsided  in  consequence 
of  subterranean  movements,  leaving  valley-like  depressions. 
3.  Profound  fractures  have  taken  place  in  connection  with 
mountain-making,  leaving  sometimes  open  rents,  as  narrow 
valleys  or  gorges. 

But,  notwithstanding  the  frequency  of  fractures,  there  are 
few  valleys  over  the  earth  that  can  be  pointed  to  as  made  in 
this  way.  Fractures  have  sometimes  determined  the  courses 
of  streams ;  but  the  stream,  thus  guided  in  its  original  course, 
has  afterward  carried  forward  its  work  of  erosion,  and  made 
the  great  valley  in  which  it  flows. 


III.  — Making   of  Hills   and    Mountains,    and   the 
attendant  effects. 

THERE  are  three  prominent  methods  of  mountain-making, 
producing  widely  different  results. 

I.    Mountains  made  by  Igneous  Ejections. 

Mountains  have  been  made  by  igneous  ejections,  especially 
by  those  of  volcanic  vents,  as  explained  on  page  64.  Thou- 
sands of  square  miles  over  the  western  slope  of  the  Rocky 
Mountains  have  been  covered  by  igneous  rocks,  and  in  Oregon 
they  have  a  thickness  of  more  than  4,000  feet;  and,  besides, 
they  form  cones  there,  whose  summits  are  10,000  to  14,440 


AND  ATTENDANT  EFFECTS.  81 

feet  above  the  sea.  The  loftiest  peak  of  the  Andes,  nearly 
23,000  feet  high,  as  already  stated,  and  numerous  others  hi  that 
chain,  were  made  by  volcanic  action.  Mount  Etna,  in  Sicily,  is 
nearly  11,000  feet  high;  two  volcanic  mountains  of  Hawaii 
are  nearly  14,000  feet  high,  and  another  is  about  10,000. 

This  is  the  least  important  of  the  methods  by  which  moun- 
tains have  been  formed. 

2.    Mountains   and    Hills   produced    by  the  Erosion  of 
Elevated   Lands. 

In  all  mountain  regions  the  lofty  summits  and  ridges  have 
been  shaped  out  mainly,  as  already  explained,  by  running  water, 
and  such  heights  are  therefore  examples  of  the  results  of  ero- 
sion on  elevated  lands.  But  the  mountain-making  is  a  little 
more  completely  the  work  of  erosion  when  a  region  of  hori- 
zontal rocks,  which  when  first  raised  was  a  lofty  plateau,  has 
undergone  long  erosion.  Owing  to  the  height,  perhaps  several 
thousand  feet,  the  torrents  which  the  rains  make  and  feed  have 
a  steep  descent,  and  therefore  great  eroding  power;  and  ulti- 
mately such  a  plateau  has  often  been  reduced  to  a  region 
of  profound  valleys  and  precipitous  ridges.  The  elevations 
described  on  page  78,  as  the  remnants  of  a  great  rock-forma- 
tion, are  examples  of  mountain  sculpture  of  this  kind.  These 
remains  are  battlemented  heights,  temples  of  mountain-dimen- 
sions, towers,  and  columns.  The  elevations  have  often  a  broad 
cap  of  harder  rock  at  top,  and  if  of  much  breadth  they  are 

4*  F 


82 


MAKING  OE  MOUNTAINS, 


Fig.  63. 


called  mesas,  from  the  Spanish  mesa,  a  table.  The  Catskills 
are  a  group  of  high  summits  3,000  to  4,000  feet  above  the 
sea-level,  carved  by  running  water  out  of  an  elevated  region 
of  nearly  horizontal  rocks.  Such  examples  are  very  common 
over  the  world.  For  in  the  changes  of  level  which  the  earth's 
crust  has  undergone  areas  have  often  been  lifted  without  much 

disturbance  of  the  beds. 

Examples  of  monumental 
forms  on  a  small  scale  oc- 
cur in  Colorado,  and  have 
given  the  name  of  Monu- 
ment Park  to  the  region. 
Pig.  63  is  a  sketch  of  a 
scene  in  it,  from  Hayden's 
Eeport  for  1873.  Such 
effects  of  erosion  may  have 
been  produced  mainly  by 
rains  and  running  water ; 
but  they  are  in  part  due 
to  the  winds  j  to  the  quiet 
work,  chemical  in  nature,  of  air  and  moisture;  to  the  alter- 
nate heating  and  cooling  of  the  surface  in  consequence  of  the 
daily  changes  of  temperature;  and,  in  frosty  regions,  or  where 
the  winters  are  cold,  to  the  freezing  of  moisture  over  the 
surface. 

Over  undisturbed  regions  of  Tertiary  and  Quaternary  for- 


Erosion  in  Monument  Park,  Colorado. 


AND  ATTENDANT  EFFECTS.  83 

mations  erosion  has  often  reduced  the  once  level  surface  to  a 
collection  of  hills.  In  some  parts  of  the  eastern  slope  and 
summit  of  the  Rocky  Mountain  region  the  Tertiary  is  worn 
into  a  labyrinth  of  valleys  and  variously  shaped  ridges,  needles, 
and  table-like  elevations. 

This  mountain-making  by  erosion  is  an  external  sculpturing 
of  the  earth's  surface,  and  not  true  mountain-making,  —  the 
subject  considered  under  the  third  head. 

3.    Mountains  made  by  Upturnings  and  Flexures  of  Rocks, 
and   Bendings  of  the  Earth's  Crust. 

Mountain  ranges  have  been  made,  for  the  most  part,  through 
bendings  of  the  earth's  crust,  and  the  upturning  and  flexures 
of  the  rocks. 

1.  Upturned  rocks.  —  The  layers  of  stratified  rocks  were,  with 
small  exceptions,  originally  horizontal,  this  being  the  position 
which  layers  of  sediment  usually  have  when  forming.  They 
are  now  very  commonly  more  or  less  upturned.  Sometimes  the 
angle  of  inclination  is  small;  but  in  most  mountain  regions 
the  beds  are  inclined  at  high  angles,  and  often  are  vertical  or 
nearly  so.  In  the  study  of  the  inclined  positions  of  strata  the 
geologist  studies  the  origin  of  mountains. 

The  inclination  of  the  beds  below  a  horizontal  plane  is  called 
the  dip;  and  the  horizontal  direction  at  right  angles  to  the 
dip  is  the  strike.  When  the  roof  of  a  house  slopes  in  oppo- 
site directions  from  a  horizontal  ridge-pole,  the  angle  of  slope 


MAKING  OF  MOUNTAINS, 


or  pitch  of  the  roof  corresponds  to  the  dip  j  and  the  direction 
of  the  ridge-pole,  to  the  strike. 

Some  of  the  positions  of  upturned  rocks  are  shown  in  the 
following  figures.     Fig.  64  represents  a  ledge  of  rocks   pro- 


Figs.  64,  65. 


65 


Upturned  strata. 


jecting  above  the  ground;  d  p  is  the  direction  of  the  dip, 
and  s  t  that  of  the  strike.  Fig.  65  represents  a  portion  of 
the  coal-formation  with  stumps  of  trees  rising  out  of  the  coal- 
beds,  which  have  lost  their  vertical  position  because  of  the 
upturning  of  the  strata. 


Figs.  66-70. 


66 


Flexed  or  folded  strata. 

2,  Flexures.  —  Pigs.  66-70   represent  flexures   or  folds  of 
the  strata,  —  such  as   are  of  common  occurrence.     The  folds 


AND  ATTENDANT  EFFECTS.  85 

in  a  mountain  region  are  sometimes  many  miles  in  span,  and 
often  one  arch  rises  beyond  another.  The  Appalachians  and 
Jura  Mountains  are  full  of  examples.  The  upward  bend  (at 
a  x  in  Figs.  66  —  69)  is  called  an  anticlinal,  from  the  Greek 
signifying  inclined  in  opposite  directions ;  and  the  downward 
bend  (at  a  x)  a  synclinal,  meaning  inclined  together,  a  x, 
a  x'  are  the  positions  of  the  axes  or  axial  planes  of  the  folds, 
a  x  an  anticlinal  axis  and  a'  x'  a  synclinal  axis.  In  Figs. 
68,  69  the  folds  are  pressed  over  beyond  a  vertical,  so  that 
the  axial  plane  makes  a  large  angle  with  a  vertical  line.  In 
Fig.  70  three  folds  are  raised  together. 

Fig.  71. 


ffl 
Section  from  the  Great  North  to  the  Little  North  Mountain,  through  Bore  Springs. 

1 1,  positions  of  thermal  springs. 

Fig.  71  represents  an  actual  section  six  miles  long,  from  a 
part  of  the  Appalachians  illustrating  well  the  flexures.  But 
it  illustrates  another  fact:  that,  since  the  flexures  were  made, 
the  region  has  been  worn  by  waters,  either  those  of  rivers  or 
the  ocean,  so  that  the  tops  of  the  flexures  are  worn  off,  and 
where  they  once  were^ there  are  now  valleys;  such  a  valley 
is  represented  in  Fig.  71,  to  the  left  of  the  middle  above 
II.  The  tops  of  such  folds  would  have  been  broken  deeply 
while  the  bending  was  in  progress,  and  the  breaks  would  have 
opened  upward;  and  therefore  these  should  be  the  parts  most 
deeply  eroded.  The  thin  black  layer  over  IV,  on  the  left, 


MAKING  OE  MOUNTAINS, 


was  once  continuous  with  IV,  near  the  middle  of  the  section; 
and  so  with  the  rest.  To  the  right  end  of  the  section  the 
beds  are  vertical. 

Another  view  of  upturned  and  eroded  rocks  as  they  occur 
at  a  locality  in  Western  Colorado   is  given  in  Eig.  72.     The 

Fig.  72. 


Upturned  strata  of  the  west  dope  of  the  Elk  Mountains,  Colorado. 

The  light-shaded  stratum,  Triassico-Jurassic  ;  that  to  the  right  of  it,  Carboniferous  ;  that  to  the  left, 
Cretaceous. 

strata  in  the  foreground  have  the  reverse  dip  of  those  more 
distant,  showing  a  twist  connected  with  the  upturning. 

Other  examples  of  folding  and  of  subsequent  degradation, 
from  the   Alleghanies,   are   illustrated  in  Pigs.    73-78.      In 

Figs.  78  -  78. 


75 


Degradation  of  a  folded  mountain  region. 

each  case  the  harder   stratum  in  the   series   determines  in  a 
large  degree  the  final  form  of  the  hill  and  the  landscape  effect 
of  the  erosion. 
Fig.  79  represents  a  still  more  remarkable  case  of  flexures 


AND  ATTENDANT  EFFECTS. 


87 


and  subsequent  erosion;  the  folded  region  lias  been  worn  away 
to  a  nearly  level  surface,  so  that  the  existence  of  flexures  is 
to  be  ascertained  only  in  vertical  sections  of  the  rocks.  Ee- 
gions  of  such  folded  rocks  are  generally  very  difficult  to  study, 
because  of  the  extensive  erosion.  Ledges  and  ridges  in  which 
the  strata  slope  only  in  one  direction  are  often  one  side  or 
part  of  a  great  fold. 

Fig.  79. 


General  view  of  folds  in  the  Archaean  rocks  of  Canada. 

3.  Fractures  and  Faults,  —  Besides  flexures,  great  and  small 
fractures  have  been  made  during  epochs  of  upturning  or 
mountain-making.  Fig.  80  represents  strata  thus  broken;  and, 
moreover,  the  beds  are  displaced  along  the  fractures.  The 
beds  numbered  1,  1,  1  were  once  a  single  continuous  layer; 


Figs.  80,  81. 


Fractures  and  Faults. 


and  so  with  the  others ;  but  at  the  time  of  fracture  there  was 
a  dropping  of  the  middle  portion,  so  that  along  each  fracture 
there  is  now  a  fault,  or  displacement.  Another  case  is  illus- 


88 


MAKING  OE  MOUNTAINS, 


trated  in  Fig.  81.  The  fault  in  a  vein  described  on  page  75 
is  another  example.  The  figures  represent  faults  or  displace- 
ments of  only  a  few  feet  or  yards;  but  in  many  faults,  pro- 
duced in  the  making  of  a  range  of  mountains,,  the  rocks  of 
one  side  of  a  fracture  have  been  pushed  up,  or  have  dropped 
down,  thousands  of  feet.  When  fractures  are  very  numerous 
over  a  region,  and  of  great  extent  and  regularity,  they  are 
called  joints. 

4  Unconformable  strata. — 'Rocks  are  often  laid  down  hori- 
zontally over  upturned  rocks;  the  layers  of  the  two  do  not 
then  conform  to  one  another;  as  in  Pig.  82,  in  which  the 

Fig.  82. 


Section  from  south  side  of  the  St.  Lawrence.  Canada,  between  Cascade  Point  and  St.  Louis  Rapids. 
i,  gneiss ;  z,  Potsdam  sandstone. 

rocks  1  and  2  are  unconformable,  while  2  and  those  overlying 
2  are  conformable.  In  the  figure  there  is  a  fault  represented 
to  the  left  of  the  middle;  and  there  are  others  farther  to 
the  left,  which  are  confined  to  the  lower  beds  (1),  and  which, 
therefore,  were  made  before  the  next  stratum  above  (2)  was 
deposited. 

5.  Earthquakes.  — The  upturning,  flexing,  and  fracturing  of 
rocks  could  not  have  taken  place  on  so  grand  a  scale  without 
sudden  shakings  or  jars  of  the  rocky  strata;  and  every  such 
jar  was  an  earthquake.  A  scratch  of  a  pin  on  the  end  of  a 


AND  ATTENDANT  EFFECTS.  89 

log  may  be  heard  by  placing  the  ear  at  the  other  end,  be- 
cause the  vibration  made  by  the  scratch  travels  along  the  log, 
and  with  great  rapidity.  A  jar  in  the  earth's  crust  or  its 
rocks  travels  in  the  same  way.  It  has  often,  in  modern  times, 
been  felt  through  a  hemisphere.  Subterranean  thunder  has 
been  a  consequence  of  it ;  and  profound  fractures  of  the  earth's 
surface,  resulting  sometimes  in  the  destruction  of  cities  and 
human  lives.  Earthquakes  occur  whenever  there  is  any  yield- 
ing or  slipping  or  fracture  of  the  rocks  beneath  the  earth's 
surface;  and  they  are  most  likely  to  occur  along  the  moun- 
tain border  of  a  continent  where  have  been  the  greatest  up- 
turnings,  and  especially  where  there  are  volcanoes  along  such 
borders. 

6.  Metamorphism.  —  The   upturning,   fracturing,  and  flexing 
attending  mountain-making  accounts  for  the  heat  required  for 
metamorphism,  and  for  the  very  wide  extent  of  most  areas  of 
metamorphic  change;  for  regions  of  metamorphism  are  regions 
of  upturned  rocks   (page  72). 

7,  Cause  of  upliftings,  fractures,  and  flexures,  and  of  mountain- 
making.  —  If  a  quire  of  paper,  lying  on  a  table,  be  pressed 
together  at  the  front  and   back   edges,   it    will  rise    into    a 
fold ;   and,  in  case  the  paper  is  a  soft  and  inelastic  kind,  into 
a  series  of  folds.     Pushing  from  below  will  make  it  bulge  up- 
ward,  but   only    lateral   pressure  will   make  a   succession   of 
folds.     The  facts  with  regard  to  flexures  in  the  rocks  of  moun- 
tain regions  prove  that  the  force  which  has  made  the  great 


90  MAKING  OF  MOUNTAINS, 

series  of  folds,  uplifts,  and  fractures  has  acted  laterally  ;  that 
is,  it  was  lateral  pressure  within  the  earth 's  crust. 

Mountain  ranges  occur  on  all  the  continents,  showing  that 
the  cause  of  uplift  and  flexure  has  been  a  universal  one;  and 
so  lateral  pressure  within  the  earth's  crust  is  a  force  neces- 
sarily universal  in  its  action.  Mountain  ranges  are  hundreds 
and  even  thousands  of  miles  in  length;  and  a  cause  thus 
universal  is  sufficient  to  have  made  all,  whatever  their  length 
or  height. 

This  lateral  pressure  is  attributed  to  the  admitted  fact 
that  the  earth  was  once  melted  throughout,  and  has  gradually 
cooled  over  its  surface  ;  and  that  the  first  crust  formed 
has  been  thickening  below  from  the  continued  cooling.  In 
cooling  from  fusion  a  rock  contracts,  losing  on  an  average 
a  twelfth  of  its  bulk ;  and  hence  continued  cooling  means 
continued  contraction  beneath  the  first-formed  crust;  and  an 
effort  to  draw  it  downward.  The  crust  would  be  necessa- 
rily put,  under  such  circumstances,  into  a  state  of  pressure 
of  every  part  against  every  adjoining  part,  like  the  pressure 
between  the  stones  of  an  arch ;  and  if  any  part  gave  way,  or 
the  crust  were  flexible  at  all,  there  would  be  uplifts,  flexures, 
breaks,  or  faults.  The  flexures  in  the  earth's  strata  are,  then, 
the  effects  of  this  lateral  pressure,  and  are  some  evidence 
as  to  its  extent  and  power. 

The  great  ranges  of  mountains  are  situated,  for  the  most 
part,  on  the  borders  of  the  oceans.  Thus  on  the  Atlantic 


AND  ATTENDANT  EFFECTS.  91 

border  there  is  the  Appalachian  chain,  while  on  the  Pacific 
stand  the  lofty  Bocky  Mountains.  Again,  in  South  America 
there  are  the  Brazilian  Mountains  on  the  east,  and  the  far 
greater  chain  of  the  Andes  on  the  west.  Other  continents 
illustrate  the  same  truth,  —  that  the  continents  have  high 
borders  and  a  low  interior,  and  also  that  the  highest  border 
faces  the  larger  ocean. 

Moreover,  the  volcanoes  of  the  continents  are,  with  few 
exceptions,  near  the  ocean,  and  far  the  greater  part  of  them 
are  on  the  borders  of  the  Pacific  or  larger  ocean  (page  67). 

These  facts  prove  that  the  breaks  and  uplifts  that  were 
made  by  lateral  pressure  in  the  earth's  crust  were  mostly 
confined  to  the  borders  of  the  oceans,  and  that  they  were 
most  extensive  on  the  sides  of  the  largest  ocean. 

A  reason  for  this  position  of  the  great  mountain  chains 
near  the  oceans  is  found  in  the  fact  that  the  crust  of  the 
earth  that  lies  beneath  the  ocean's  bed  is  lower  in  level  than 
that  of  the  land,  and  the  basin-like  depression  has  rather 
abrupt  sides  toward  the  continents.  Owing  to  this  the  action 
of  the  lateral  pressure  from  the  direction  of  the  ocean  was 
obliquely  upward  against  the  land,  and  therefore  just  what  was 
required  to  push  up  the  borders  of  the  continents  into  moun- 
tains, or  to  produce  flexure  after  flexure  in  the  yielding  rocks, 
or  to  break  them  and  give  outflow  to  floods  of  lava. 

Mountain  chains  are  the  result  of  more  than  one  moun- 
tain-making process.  A  single  example  will  suffice  to  illus- 


92  MAKING  OF  MOUNTAINS. 

trate  this  truth.  The  range  of  elevated  land  from  Labrador 
to  Alabama  is  called  the  Appalachian  chain.  But  the  Adi- 
rondacks,  the  Highlands  of  New  Jersey,  and  portions  of  the 
Blue  Eidge  of  Pennsylvania  and  Virginia  were  made  long 
before  the  rest.  The  Green  Mountains  east  of  the  Adiron- 
dacks  were  next  raised;  then,  after  another  immense  period 
of  time  had  passed,  at  the  close  of  the  Carboniferous  age,  the 
Alleghanies  from  New  York  to  Alabama,  west  of  the  line  of 
the  Blue  Eidge  and  Highlands,  were  completed.  Thus  the 
Appalachian  chain  was  a  result  of  a  succession  of  mountain- 
making  efforts,  one  producing  one  part,  and  the  rest  others. 
The  process  did  not  go  on  twice  along  just  the  same  range 
of  country,  but  to  one  side  of  the  preceding,  either  east  or 
west.  Since  the  completion,  the  country  has  been  raised  as  a 
whole  by  a  gentle  bending  upward  of  the  earth's  crust,  — 
the  lateral  pressure  in  this  case,  after  the  mountains  were 
made,  and  their  rocks  folded  and  consolidated,  and  the  crust 
thereby  stiffened,  producing  a  slight  flexure  of  the  crust  and 
not  any  folding  of  strata. 

After  the  making  of  the  Alleghanies  there  was  mountain- 
making  of  a  different  kind  more  to  the  eastward  in  the 
course  of  the  next  age.  Along  the  regions  of  the  Bay  of 
Fundy,  the  Connecticut  Yalley  south  of  New  Hampshire,  and 
a  long  range  of  country  from  the  Palisades  on  the  Hudson 
through  New  Jersey  and  Pennsylvania  into  North  Carolina 
(each  region  parallel  to  the  part  of  the  Appalachian  chain  west 


MAKING  OF  CONTINENTS.  93 

of  it),  where  several  thousand  feet  of  sandstone  had  been  de- 
posited, there  were  made,  finally,  along  with  a  small  upturning 
of  the  strata,  a  vast  number  of  great  fractures  of  the  earth's 
crust,  the  fractures  deep  enough  to  let  out  melted  rock;  and 
this  rock,  cooled,  constitutes  the  Palisades  on  the  Hudson, 
Mount  Holyoke  in  Massachusetts,  and  various  other  trap 
ridges  in  the  Connecticut  Yalley,  Nova  Scotia,  and  the  more 
southern  sandstone  regions.  Here  the  lateral  pressure  pro- 
duced little  upturning,  but  much  fracturing,  with  extensive 
igneous  ejections ;  and  this  exemplifies  a  second  method  of 
action  in  mountain-making,  a  method  which  was  most  com- 
mon in  the.  later  end  of  geological  time,  when  the  earth's 
crust  had  become  too  stiff  to  bend  easily.  After  this  epoch 
of  disturbance  there  were  no  other  general  upturnings  along 
the  Atlantic  border  of  the  continent.  Mountain-making  was 
there  ended  long  before  it  was  on  the  Pacific  or  Eocky 
Mountain  side,  and  long  before  it  was  in  Europe.  Neither 
these  mountains  nor  the  Alps,  Pyrenees,  or  Himalayas  were 
finished  before  the  close  of  the  Tertiary ;  and  the  grandest  of 
igneous  ejections  in  the  world  belong  to  the  same  age,  the 
last  before  Man. 

Another  principle  connected  with  mountain-making  remains 
for  consideration.  It  will  be  best  understood  after  some  of 
the  facts  in  geological  history  have  been  reviewed;  the  dis- 
cussion of  it  is  therefore  deferred  to  the  pages  treating  of  the 
formation  of  the  Alleghany  Mountains.  (See  pages  171,  208.) 


94  CONCLUSION. 


7.  Making  of  continents  and  the  oceanic  depression.  —  Con- 
traction from  cooling  also  gives  a  reason  for  the  existence  of 
the   great   depressions   occupied   by   the   oceans  ;   for,  on   this 
view,  they  are  the  parts  of  the  earth's  crust   that   have  sunk 
most  with   the  progressing  contraction,  —  the  parts,  therefore, 
which  were   last   stiffened,  when  the   crust  was   in  process  of 
formation;   while  the   continents   were   the   portion   that  con- 
tracted least,  or  which  first  became  solid. 

8.  Conclusion.  —  There  is  thus,   in  the  single  fact  that  the 
earth  is,  and  ever  has  been,  a  cooling  globe,  and  therefore  uni- 
versally a  contracting  globe,  an  explanation  (1)  of  the  gentle 
oscillations    of  level   in    the    earth's    surface   that    have    been 
quietly  going  on  through  all  past  time;  (£)  of  the  upturnings, 
flexures,  fractures,  faults,  and  upliftings  of  strata,  and  the  bend- 
ings  of  the  earth's  crust,  which  have  resulted  in  the  making  of 
the  great  mountain  chains  of  the  globe ;   (3)  of  the  opening  of 
fractures  down  to  the  deep-seated  regions  of  fire  giving  exit 
to  floods  of  liquid  rock  and  producing  volcanoes;   (4)   of  the 
alteration  of  rocks,  or  their  metamorphism,  changing  the  rude 
sand-beds  and  mud-beds  into  crystalline  rocks,  and  filling  fis- 
sures with  veins  of  ores   and   gems;   (5)   of  earthquakes,  the 
great  earthquakes  and  the  larger  part  of  the  smaller  ones ;  and, 
finally,  (6)   an  explanation  of  the  origin  of  continents. 

It  may  be  thought  that  by  thus  referring  to  secondary  causes 
the  making  and  crystallizing  of  rocks,  the  placing  and  raising 
of  mountain  chains,  and  even  the  defining  of  continents,  we 


CONCLUSION.  95 


leave  little  for  the  Deity  to  do.  On  the  contrary,  we  leave  all 
to  him.  There  is  no  secondary  cause  in  action  which  is  not 
by  his  appointment  and  for  his  purpose,  no  power  in  the  ma- 
terial universe  but  his  will.  Man's  body  is,  for  each  of  us,  a 
growth;  but  God's  will  and  wisdom  are  manifested  in  all  its 
development.  The  world  has  by  gradual  steps  reached  its  pres- 
ent perfected  state,  suited  in  every  respect  to  man's  needs  and 
happiness,  —  as  much  so  as  his  body;  and  it  shows  throughout 
the  same  Divine  purpose,  guiding  all  things  toward  the  one 
chief  end,  —  Man's  material  and  spiritual  good. 


PART   III. 

HISTORICAL  GEOLOGY. 
Subjects  and  Subdivisions. 

HISTORICAL  GEOLOGY  treats  of,  — 

1.  The  succession  in  the  formation  of  the  rocks  of  the  earth, 
and  in  the  conditions  under  which  they  were  made. 

£.  The  progress  in  the  continents,  from  their  small  begin- 
nings to  their  present  magnitude. 

3.  The  changes  of  level  ever  going  on,  and  the  raising  of 
mountains   at   long  intervals  in  the   course   of  the   ages,  the 
highest  and  longest  in  the  last  of  those  ages  just  before  the 
era  of  Man. 

4.  The  multiplication  of  rivers   as  the  dry  land  extended, 
and  thereby  the   excavation   of  valleys,  the   shaping   of   lofty 
ridges  giving  grandeur  to  the  mountains,  and  the  spreading  of 
the  lower  lands  with  soil  and  fertility. 

5.  The  changes  in  climate,  from  the   universal  warmth   of 
the  Archaean  world  to  the  existing  variety  of  heat  and  cold. 

6.  The  succession  in  the  species  under  the  two  kingdoms 


HISTORICAL  GEOLOGY.  97 

of  life  —  Plants   and   Animals  —  from   the   simpler   forms   of 
early  time  to  Man. 

The  rocks  are  sometimes  spoken  of  as  the  leaves  of  the 
geological  record.  But  these  rocks  are  in  various  lands,  here 
some  and  there  others;  and  how  can  they  be  brought  into 
order '  so  as  to  make  a  continuous  history  worthy  of  confi- 
dence ?  The  case  would  have  been  hopeless  were  it  not  for  one 
branch  of  this  history,  —  that  relating  to  the  progress  of  life. 
There  has  been,  as  above  intimated,  a  succession  in  the 
species  of  plants  and  animals  that  have  lived  upon  the  globe. 
The  earliest  kinds  were  followed  by  others,  and  these  by  still 
others,  and  so  on,  through  age  after  age,  before  the  final  ap- 
pearance of  Man.  The  plants  and  animals  that  lived  in  the 
successive  periods  left  their  relics  —  that  is,  stems  or  leaves, 
shells,  corals,  bones,  and  the  like  —  in  the  mud  or  sand  of 
the  sea-bottom,  sea-shore  flats  and  beaches,  and  in  other  depos- 
its of  the  era;  and  these  sand-beds  and  mud-beds  are  now 
the  rocks  of  those  periods.  Hence  in  the  rocks  of  one  era 
we  find  different  relics,  or  fossils,  from  those  of  the  preceding 
or  following  era.  Geologists  have  ascertained  the  kinds  that 
belong  to  the  successive  rocks,  or  eras,  of  the  world ;  so  that, 
if  they  come  upon  an  unknown  rock  with  fossils,  in  a  coun- 
try not  before  studied,  it  is  only  necessary  to  compare  the 
fossils  found  with  the  lists  already  made  out. 

Eor  a  very  long  part  of  early  time  after  life  was  abundant 
there  were  no  fishes  in  the  world.  The  discovery  of  a  fossil 

5  G 


98  HISTORICAL  GEOLOGY. 

fish  in  a  bed  of  rock  is,  hence,  evidence  that  the  bed  does 
not  belong  to  the  formations  of  that  early  time,  but  to 'one 
of  some  later  period.  After  the  first  appearance  of  fishes  the 
kinds  changed  with  the  progress  of  time;  so  that  if,  in  the 
case  of  our  discovery,  we  can  ascertain  the  tribe  to  which  the 
fossil  fish  we  have  obtained  belonged,  we  can  then  decide 
approximately  the  age  of  the  rock  which  afforded  it.  No  her- 
ring, cod,  and  salmon  are  known  to  have  existed  until  near 
the  last  of  the  geological  ages  ;  and  if  the  species  turned 
out  to  be  related  to  these,  we  should  conclude  that  the  rock 
was  among  the  later  in  geological  history;  and  a  determination 
of  the  species  might  lead  to  the  precise  epoch  to  which  it 
pertained.  Bones  of  beasts  of  prey,  cattle,  and  horses  are 
found  only  in  rocks  of  the  last  two  geological  ages. 

Thus,  owing  to  the  succession  of  life  on  the  globe,  the 
geologist  is  enabled  to  arrange  the  fossiliferous  rocks  in  the 
order  of  their  formation,  —  that  is,  the  order  of  time. 

If  a  stratum  in  one  region  contains  no  fossils,  or  if  its  fossils 
have  been  obliterated  by  heat  producing  metamorphism,  the 
stratum  is  traced  by  the  geologist  to  another  region,  with  the 
hope  of  there  discovering  fossils,  or  at  least  of  finding  them  in 
an  underlying  or  overlying  stratum.  In  this  and  other  ways 
doubts  are  gradually  removed,  and  the  true  succession  in  any 
region  is  made  out. 

The  history  has  thereby  been  divided  into  four  grand  sec- 
tions :  — 


HISTORICAL  GEOLOGY.  99 

I.  ARCHAEAN  TIME;  that  is,  beginning  time;   the  word  Ar- 
chaan  is  from  the  Greek  for  beginning. 

II.  PALEOZOIC   TIME,  or   the  era  of  the   ancient   forms  of 
life;  Paleozoic  being  from  the  Greek  for  ancient  and  life. 

III.  MESOZOIC  TIME,  or  the  era  of  mediaeval  forms  of  life; 
Mesozoic,  from  the  Greek,  signifying  middle  and  life. 

IV.  CENOZOIC  TIME,  or   the   era  of  the   more  recent  forms 
of  life ;   Cenozoic  signifying  recent  and  life. 

Paleozoic  time,  which  was  probably  at  least  threefold 
longer  than  all  later  time,  has  been  divided  into  three  ages : 
(1)  the  SILURIAN,  or  AGE  OF  INVERTEBRATES;  (2)  the  DE- 
VONIAN, or  AGE  OF  FISHES;  and  (3)  the  CARBONIFEROUS,  or 
AGE  OF  COAL  PLANTS.  Mesozoic  time  corresponds  to  the 
AGE  OF  EEPTILES.  Cenozoic  time  is  divided  into  two  ages, 
called  (1)  the  TERTIARY,  or  AGE  OF  MAMMALS  ;  and  (2)  the 
QUATERNARY,  or  AGE  OF  MAN. 

The  kingdom  of  Animals  has  five  great  branches,  or  subdi- 
visions, called  sub-kingdoms.  These  are, — 

1.  Protozoans:   Microscopic   species,  with  no  internal   organ 
beyond  a  stomach,  and  none  external  unless  hair-like  or  thread- 
like appendages.     The  Rhizopods  and  Sponges,  of  which  fig- 
ures are  given  on  pages  33,  39,  are  here  included.     Sponges 
are  large,  but  only  because  each  is  an  aggregate  of  a  great 
number   of  the   minute   animals.     The  word   Protozoan,  from 
the  Greek,  means  first  or  simplest  animal. 

2.  Radiates:   Animals  having  a  radiated  structure,  that  is, 


100 


HISTORICAL  GEOLOGY. 


Fig.  83. 


Astrsea  pallida  D. 

having  the  parts  arranged  radiately  around  a  centre,  .with  the 
mouth  at  or  near  the  centre  :  as  in  polyps,  the  animals  of 
corals,  which  look  very  much  like  flowers  on  account  of  the 
radiate  arrangement.  Each  one  of  the  expanded  polyps  in 
this  figure  of  a  living  coral  (Fig.  83)  shows  well  the  radiate 
character.  The  Crinoids,  represented  on  page  31,  are  other 
examples  of  Radiate  animals. 

3.  Mollusks:   as   the   Oyster,   Clam,    Snail,  and  Cuttle-fish; 
having   a   soft,  fleshy,  bag-like   body,  with  sometimes   an   ex- 
ternal shell  for  its  protection,  or  an  internal  bone  or  shell  to 
give  a  degree  of  firmness  to  the  fleshy  body. 

4.  Articulates:    as  the  My,  Butterfly,  Beetle,  and  other  in- 
sects, the  Spiders  and  Centipedes,  the  Lobster,  Crab,  and  other 
Crustaceans,  and  the  Worms :   animals  having  the  body  made 


HISTORICAL  GEOLOGY.  101 

up  of  segments  or  parts  jointed  together,  and  having  the  legs 
and  feelers  jointed.  A  lobster  shows  well  the  jointing  of  the 
body  and  of  all  its  limbs.  Articulate  means  jointed.  The 
Lobster,  Shrimp,  Crab,  and  some  other  related  animals  are 
called  Crustaceans  because  they  have  a  crust-like  exterior 
sometimes  called  the  shell. 

5.  Vertebrates:   as   Fishes;   Progs,  Lizards,  Snakes,   Croco- 
diles,   Turtles,    and    other    Eeptiles ;    Birds ;    the    Dog,    Cat, 

Fig.  84. 


Vertebrate. 
Pterodactylus  crassirostris  (X  l/4). 


Horse,  Ox,  Whale,  and  other  Mammals;  animals  having  in- 
ternally, along  the  back,  a  series  of  bones  making  together 
the  vertebral  column.  In  Pig.  84,  representing  one  of  the 
Flying  Eeptiles  of  ancient  time,  the  vertebral  column  is  seen 
extending  from  the  head  into  the  tail.  Each  separate  bone 


102  HISTORICAL  GEOLOGY. 

of  the  column  is  called  (from  the  Latin)  a  vertebra.  The 
great  nerve  of  the  body,  called  the  spinal  cord,  lies  concealed 
in  a  tubular  bone-sheathed  cavity  along  the  upper  side  of  the 
column;  and  below  the  column  there  are  the  ribs  and  the 
cavity  for  the  stomach  and  other  viscera.  The  Mammals  are 
those  Vertebrates  that  suckle  their  young,  as  the  word,  from 
the  Latin,  implies.  They  are  the  highest  of  Vertebrates,  and 
include  Man  as  well  as  the  other  animals  above  mentioned. 

Protozoans,  Radiates,  Mollusks,  and  Articulates  are  often 
together  called  Invertebrates,  that  is,  not  Vertebrates. 

In  the  table  above  (page  99),  the  expressions  Age  of  In- 
vertebrates, Age  of  Fishes,  Age  of  Reptiles,  Age  of  Mammals, 
are  not  to  be  understood  as  implying  that  the  several  groups 
of  animals  mentioned  were  confined  to  the  age  named  after 
them,  but  only  that  they  were  the  highest,  and  therefore  the 
characteristic,  species  of  the  age. 

Pishes  began  before  the  Silurian  Age  was  quite  completed, 
and  continued  thence  through  geological  time;  but  until  the 
close  of  the  Devonian,  or  nearly  so,  they  were  the  highest  of 
living  species. 

In  the  Silurian,  until  near  its  close,  there  were  only  Inver- 
tebrates. 

In  the  Age  of  Reptiles,  the  class  of  Reptiles,  which  began 
in  the  preceding  age,  had  larger,  more  numerous,  and  higher 
species  than  before  or  afterward;  the  Age  was  eminently  the 
Age  of  Eeptiles,  the  type  having  reached  its  maximum  then, 
that  is,  having  culminated. 


HISTORICAL  GEOLOGY.  103 

Mammals  of  a  low  order,  called  Marsupials,  existed  in  the 
Age  of  Reptiles;  but  in  the  Age  of  Mammals  the  Reptiles 
were  comparatively  few,  and  true  Mammals  were  the  highest 
or  dominant  race. 

Again,  the  Age  of  Coal-plants  was  not  the  only  age  in 
which  coal-plants  lived  and  coal  was  made;  but  that  which 
was  most  remarkable  for  the  making  of  coal-beds,  and  espe- 
cially for  coal-making  plants  of  the  tribe  of  Acrogem,  the 
highest  of  Cryptogams  or  Elowerless  plants,  such  as  Ferns, 
Ground-Pines  or  Lycopods,  and  Horse-tails  or  Equiseta,  which 
then  grew  to  the  size  of  tall  shrubbery  and  forest-trees.  In 
later  ages  also  coal-beds  were  made,  but  of  less  extent,  and 
mainly  out  of  other  kinds  of  plants.  The  Carboniferous  age 
is  often  called  the  Age  of  Acrogens. 

Thus  the  Ages  are  named  after  the  tribes  of  each,  that  were 
highest  in  grade,  or  those  that  were  most  characteristic. 

During  an  age  changes  of  level,  or  catastrophes  of  some 
other  kind,  have  at  intervals  produced  extensive  exterminations 
of  species  over  a  continental  sea,  and  also  abrupt  changes  in 
the  kinds  of  rock-deposits  in  progress,  if  not  also  upturnings 
of  strata.  Each  age  in  the  geological  history  of  any  continent 
has  consequently  its  natural  subdivisions,  which  are  called  pe- 
riods. 

The  following  table  gives  a  general  view  of  the  successive 
ages,  with  some  of  the  subdivisions  that  have  been  adopted, 
the  first  in  time  being  at  the  bottom. 


104 


HISTORICAL   GEOLOGY. 


Ages. 

American. 

British. 

SUBDIVISIONS. 

SUBDIVISIONS. 

rS.  Recent. 

Recent. 

[  2.  Quaternary  

.  .  .  J  2.  Champlain. 

Champlain. 

CENOZOIC...  J 

1  X  Glacial. 

Glacial. 

1 

f3.  Pliocene. 

Pliocene. 

1  .!«  Tertiary. 

J     r»'     if 

. 

1  •  •  <  A.  Miocene. 

Miocene. 

LI.  Eocene,  including 

2.  Alabama  group,  i 

1.  Lignitic  group,  j 

.    Eocene. 

HESOZOIC Eeptilian. 


PALEOZOIC,  j 


3.  Carboniferous.. 


2.  Devonian 


-3.  Cretaceous.  Cretaceous. 

r  Jurassic,  including 

2.  Jurassic J      3.  Wealden. 

2.  Oolyte. 

1.  Lias. 
Triassic. 
Permian. 
Carboniferous. 
Mountain  limestone. 


1 


1.  Silurian. 


Upper. 


Lower. 


1.  Triassic. 
C3.  Permian. 
•j  2.  Carboniferous. 
L  1.  Subcarboniferous. 
[4.  Catskill. 

J  3.  Portage  and  Chemung.  I 
I  2.  Hamilton. 
^1.  Comiferous.  J 

{4.  Oriskany.                1 
3.  Lower  Helderberg.J" '  Ludl™  ?™P- 
2.  Salina.    1 
,    _T.  \ Wenlock  group. 

1.  Niagara.] 

C  3.  Trenton.  TLlandeilo  and  Balagroups. 

•<  2.  Canadian.  -I  Tremadoc  and  Skiddaw  slates. 

LI.  Prim'lorCamb'n.  [primordial  or  Cambrian. 


AECHJEAN. 


The  accompanying  map  (Fig.  85)  shows  the  positions  of 
the  rocks  of  the  successive  ages  over  part  of  North  America, 
so  far  as  they  are  open  to  view.  The  markings  indicating 
the  age  of  the  rocks  of  the  several  areas  are  explained  on  the 
map.  The  black  areas  are  the  great  coal  areas  of  the  conti- 
nent. The  portions  left  in  white  are  those  the  age  of  which 
is  not  ascertained. 


106  HISTORICAL  GEOLOGY. 


I.— Archaean  Time. 

THE  first  condition  of  the  earth  about  which  geology  gives 
any  hint  is  that  of  a  liquid  globe,  like  the  sun.  The  earth 
has  the  form  of  a  sphere  flattened  at  the  poles,  and  as  the 
amount  of  flattening  is  closely  that  which  such  a  liquid  globe 
would  take  as  a  consequence  of  its  revolution,  this  fact  is 
thought  to  be  evidence  of  an  original  liquid  state.  Other 
evidence  is  found  in  the  crystalline  character  of  the  oldest 
rocks;  in  the  fact  that  many  spheres  in  space,  like  the  sun, 
are  still  in  a  liquid  state;  and  in  the  condition  of  the  moon, 
which  is  like  such  a  globe  cooled  until  its  surface  is  all 
craters  and  scoria. 

Admitting  that  the  earth  has  cooled  from  fusion,  we  are 
warranted  in  concluding  that,  whenever  the  vapors  began  to 
settle  over  the  solidified  but  still  hot  crust,  there  to  make 
oceans,  the  rocks  exposed  to  the  heated  and  acid  waters  would 
have  been  everywhere  eroded  by  the  chemical  action  of  these 
waters,  and  by  this  means  they  would  have  been  covered  after 
a  while  with  new  rocks.  And  over  those  regions  where  there 
were  emerged  or  submerged  rocks  within  reach^of  the  waves, 
the  work  of  the  waves  in  making  gravel,  sand,  and  mud 
would  have  been  added  to  that  of  the  chemical  action. 

By  such  means  the  original  rock  of  the  cooled  crust  would 
have  become  nearly  or  entirely  concealed  by  new  deposits; 


ARCH^AN  TIME.  107 


and  it  is  questioned  whether  any  part  of  it  is  now  exposed 
to  view.  The  rocks  made  out  of  that  crust  —  not  those  of 
the  original  crust  itself  —  are  therefore  the  Archaean  rocks 
of  geology. 

I.    Distribution. 

The  Archaean  rocks  of  North  America  cover  a  large  sur- 
face over  the  northern  portion  of  the  continent,  and  also  some 
narrow  areas  elsewhere  along  the  courses  of  existing  moun- 
tains. In  the  accompanying  map  (Pig.  86)  the  white  areas 
are  the  regions  of  exposed  Archaean  rocks.  The  largest  ex- 
tends from  Lake  Superior  northwest  to  the  Arctic  seas  and 
northeast  to  Labrador.  It  has  the  shape  of  the  letter  V,  and 
Hudson's  Bay  is  included  within  the  arms  of  the  V.  A 
peninsula  from  it  extends  down  into  Northgrn  New  York, 
including  there  the  region  of  the  Adirondacks.  Other  Ar- 
chaean ranges  are  the  Highlands  of  New  Jersey,  portions  of 
the  Blue  Eidge  of  Pennsylvania,  Virginia,  and  the  region 
farther  southwest  (and  including  the  Black  Hills  of  North 
Carolina) ;  small  areas  in  New  England,  and  one  or  more  on 
the  Atlantic  border  south  of  New  York;  a  large  area  south 
of  Lake  Superior ;  and  the  crest  range  of  the  Eocky  Moun- 
tain region,  including  the  Wind-Eiver  Mountains  and  the 
eastern  range  in  Colorado. 

The  arms  of  the  great  V,  or  original  nucleus  of  the  conti- 
nent, are  parallel  respectively  to  the  Atlantic  and  Pacific  coast 


108 


HISTORICAL   GEOLOGY. 


lines;  the  other  narrower  areas  follow  the  courses  of  the  great 

mountain  chains,  and  are  parallel  to  the  same  lines.     Geology 

thus  affords  a  demonstration  that  even  in  Archaean  time  the 

C  great  outlines  of  the  continent  were   denned,  and  that  all  fu- 

• 

NL   I  ture   progress   was   carried   forward  by   working   on   the   plan 


thus  early  laid  down.  The  rest  of  the  continent  was  under 
wate"r  (and  perhaps  also  some  of  the  ridges  just  referred  to), 
but  it  probably  lay  at  no  great  depth. 

Archaean  areas  exist  also  in  Scandinavia,  Bohemia,  Scotland, 


ARCH.EAN  TIME.  109 


and  some   other  regions.     The  facts   prove   that  in  Archaean  j 
time   the   ocean   and    continents    were,   in    the    main,   already   ] 
outlined.     "The   waters"   of  the   world  had  been   "gathered 
into  one  place/''  and  "the  dry  land"  had  "appeared." 

2.    Rocks. 

The  Archaean  rocks  comprise  gneiss  and  granite,'  syenyte, 
syenytic  gneiss,  and  other  hornblende  rocks,  with  chloritic 
rocks,  quartzyte,  limestone,  and  other  kinds. 

They  include  immense  beds  of  iron  ore,  some  of  them  100 
to  200  feet  in  thickness,  vastly  exceeding  any  in  later  times; 
for   the   Archaean   was   the   iron    age   in   the    earth's    history.  J  ^ 
These  beds  of  ore   occur  in  Northern  New  York,  Southern 
New  York  and  Northern  New  Jersey,  Canada,  the  Marquette 
region  south  of  Lake  Superior,  in  Missouri,  where  there  are 
what   are   called   iron   mountains,  and  in  many   other   places. 
The  beds  of  ore  (i,  Fig.  87)  alternate  with 
beds  of  quartzyte  and  crystalline  schists 
or  slates,  and  lie  between  beds  of  gneiss 
and  hornblendic  gneiss,  or  other  rocks  of 
the  era,  as  illustrated  in  the  annexed  cut      Beds  of  iron  ore 

County,  New  York. 

representing  a   section  in  Essex  County, 
New   York.     Hornblende  contains  much  iron,  and  this  is  the 
reason  why  it  is  so  common  a  constituent  of  Archaean  rocks. 
The    rocks   were    originally    sedimentary    deposits;    for   the 
gneiss,  quartzyte,  and   schists   are,  as   explained  on  page  71, 


110  HISTORICAL  GEOLOGY. 

altered  or  metamorphic  sedimentary  rocks.  They  were  origi- 
nally deposits  of  gravel, .  sand,  and  mud  made  by  the  ocean. 
The  stratification  in  the  gneiss  and  other  rocks  is  the  original 
stratification  of  the  fragmental  beds. 

Like  other  sedimentary  deposits  the  rocks  were  laid  down  in 
horizontal  beds.  But  they  are  now  upturned  at  all  angles,  and 
often  foHed,  showing  thereby  that,  subsequent  to  their  deposi- 
tion, they  underwent  the  great  disturbances  that  attend  moun- 
tain-making. Fig.  88  shows  the  general  condition  of  the  rocks 

Fig.  88. 


General  view  of  folds  in  the  Archaean  rocks  of  Canada. 

in  the  Archaean  regions  of  Canada.  The  Archaean  mountains, 
including  the  Adirondacks,  the  New  Jersey  Highlands,  the  moun- 
tains of  Scandinavia,  and  others,  were  then  made,  if  not  in  part 
earlier.  The  original  height  of  these  mountains  may  have  been 
many  thousands  of  feet  greater  than  it  is  now,  for  all  the  earth's 
agencies  of  destruction  have  been  engaged  in  the  work  of  level- 
ling them,  ever  since  that  first  of  the  geological  ages. 

Many  Archaean  rocks  much  resemble  the  crystalline  rocks  of 
later  time,  and  as  both  are  without  fossils,  they  may  be  easily 
confounded. 

The  occurrence  of  beds  of  iron  ore  scores  of  feet  thick  is 
one  means  of  distinguishing  areas  of  Archaean  age.  The  ore 


ARCH^AN  TIME.  Ill 


often  contains  some  titanium,  and  this  is  not  common  in  iron  \  V 
ores  of  later  date.     Coarse  syenitic  rocks  and  labradorite  rocks  <* 
are  characteristic  of  many  Archaean  regions,  if  not  exclusively 
Archaean. 

Sure  evidence  of  Archaean  age  is  obtained  when  fossiliferous 
beds  of  the  lowest  Silurian  are  observed  overlying  unconform- 
ably  upturned  crystalline  rocks,  as  in  Fig.  89.  Here  the  nearly 

Fig.  89. 


Section  from  south  side  of  the  St.  Lawrence,  Canada,  between  Cascade  Point  and  St.  Louis  Rapids, 
i.  Gneiss ;  2,  Potsdam  sandstone. 

horizontal  Silurian  beds  referred  to,  No.  2  and  those  above, 
were  laid  down  after  the  beds  below  were  made,  and  also 
after  their  upturning;  and  consequently  the  evidence  that  the 
latter  belong  to  anterior  time  is  unquestionable. 

3.  Life. 

The  earlier  part  of  Archaean  time  was  necessarily  without 
life;   for  until   the   rocks   and   seas   had   cooled   down  to   the 
temperature  of  boiling  water,  life  was  hardly  possible.     Plants 
of  the  lowest  orders  can  bear  a  higher  temperature  than  the)  *J 
lowest  of  animals,  and  were  probably  the  first  living  species. 

Although  the  evidence  is  not  conclusive  that  either  plants 
or  animals  were  living  in  the  Archaean  seas,  —  since  if  fossils 
once  were  present  in  the  rocks,  they  have  been  obliterated  by 


112  HISTORICAL  GEOLOGY. 

the  crystallization  of  the  beds,  —  the  existence  then  of  the  sim- 
plest kinds  is  thought  to  be  highly  probable.  Some  of  the 
beds  contain  great  quantities  of  graphite,  the  material  of  which 
lead-pencils  are  made.  Now  (1)  graphite  is  nothing  but  car- 
bon (page  9),  the  essential  principle  of  mineral  coal,  and  (2) 
mineral  coal  was  formed  from  plants;  moreover  (3)  mineral 
coal  has  been  found  in  crystalline  rocks  converted  into  graphite. 
Here,  then,  is  evidence  favoring  the  probable  existence  of 
plants;  and  if  of  any,  of  Sea-weeds,  since  the  Lower  Silurian 
has  afforded  relics  of  no  plants  but  Sea-weeds.  Along  with 
true  Sea-weeds  there  were  probably  Diatoms,  as  these  minute 
species  are  the  simplest  of  water-plants. 

The  occurrence  of  limestone  strata  is  also  thought  to  favor 
the  idea  of  the  presence  of  plants  or  animals,  since  the  lime- 
stones of  the  world  are  almost  all  of  organic  origin.  Masses 
somewhat  coral-like  in  texture  have  been  described  as  fossils, 
under  the  name  of  Eozoon  (from  the  Greek  for  dawn-life),  and 
referred  to  the  group  of  Ehizopods,  described  on  page  32.  But 
there  is  doubt  as  to  their  being  true  fossils,  some  regarding 
them  as  of  mineral  origin.  Ehizopods  are  the  simplest  of  all 
animal  life,  and  the  kind  most  likely  to  have  been  associated 
with  Diatoms  over  the  sea-bottom. 

Whenever  the  earliest  plant,  however  minute,  was  created, 
a  new  principle  —  that  of  life  —  was  introduced,  which  should 
subordinate  physical  forces  to  its  uses.  Progress  in  a  system 
of  life  became  thereafter  the  subject  of  chief  interest  in  the 
world's  history. 


SILURIAN  AGE. 


113 


II.  —  Paleozoic  Time. 

I.  Silurian  Age,  or  Age  of  Invertebrates. 

THE  term  Silurian  comes  from  a  region  in  Wales  where  the 
rocks  occur,  and  which  was  formerly  occupied  by  a  tribe  of 
ancient  Britons  called  the  Silures.  The  age  is  divided  into 
the  era  of  the  Lower  Silurian  and  that  of  the  Upper  Silurian. 

Fig.  90. 


Archaean  Map  of  North  America. 


The  map  of  the  Archaean  dry  land,  here  repeated,  shows  to 
the  eye  the  part  of  the  North  American  continent  over  which 


114 


PALEOZOIC  TIME. 


Fig.  91. 


Geological  Map  of  England. 

The  areas  lined  horizontally  and  numbered  i  are  Silurian  Those  lined  vertically  (2),  Devonian.  Those 
cross-lined  (3),  Subcarboniferous.  Carboniferous  (4),  black.  Permian  (5).  Those  lined  obliquely  from 
right  to  left,  Triassic  (6),  Lias  (7  a),  Oolyte  (7  6),  Wealden  (8),  Cretaceous  (9).  Those  lined  obliquely  from 
left  to  right  (10,  n),  Tertiary.  A  is  London,  B,  Liverpool,  C,  Manchester,  D,  Newcastle. 


the  following  Silurian  beds  might  have  been  spread  out:  for 


LOWER  SILURIAN.  115 


the  beds  are  all  marine,  and  must  have  been  made  in  the  part 
covered  with  water,  —  the  shaded  part  in  the  map.     The  cir- 
cumstances were  in  the  main  similar  on  the  other  continents. 
In  Europe  (Great  Britain  included)  the  Archaean  dry  land  lay( 
mostly  to  the  northwest,  and  the  larger  part  of  the  rest  of  the> 
continent  was  receiving  marine  deposits. 

The  areas  in  North  America,  east  of  the  Rocky  Mountain 
region,  and  over  which  Silurian  rocks  are  exposed  to  view, 
are  those  which  are  lined  horizontally  in  the  map  on  page  105. 
The  Silurian  regions  in  England  are  distinguished  in  the  same 
way  on  the  accompanying  map  (Fig  91) ;  they  are  confined  to 
Western  England  and  Wales. 

1.    Lower  Silurian. 
1.  Bocks. 

The  rocks  of  the  Lower  Silurian  era  are  mainly  sandstones]\  x 
shales,  conglomerates,  and  limestones. 

The  same  is  true  for  all  succeeding  eras  in  geological  his- 
tory; for  sand-beds  (the  source  of  sandstones),  mud-beds  (the 
source  of  shales  and  argillaceous  sandstones),  and  limestones 
have  been  always  in  progress  from  this  time  onward  in  some 
part  of  each  continental  region.  Moreover,  sand-beds  have 
never  been  forming  in  any  region  without  the  making  of  mud- 
beds  in  the  waters  not  far  distant,  just  as  now  happens  along 
sea-shore  regions ;  for  the  grinding  which  produces  the  former 
produces  also  the  latter.  Nevertheless,  the  continental  areas 


116  PALEOZOIC  TIME. 


over  which  sand-beds,  mud-beds,  and  limestones  were  accu- 
mulating have  varied  greatly  through  the  successive  periods, 
owing  to  variations  in  level  and  other  causes;  and  at  times 
the  larger  part  of  the  continental  sea  has  been  given  up  to 
limestone-making. 

The  following  is  the  succession  of  Lower  Silurian  rocks  in 
North  America. 

1.  In   the   early  part    of   the   era,   called   the   Primordial 
(meaning  the  first  in  order] ,  sand-beds  —  now  called  the  Pots- 
dam sandstone,  from  a  locality  in  Northern  New  York  —  were 
spread  out  over  wide  areas  in  North  America,  and  especially 
about  the  shores  of  the  Archaean  dry  land ;  but  shales  and  lime- 
stones were  forming  in  some  places  more  or  less  remote  from 
these  shores. 

These  earliest  Silurian  sandstones  and  shales  have  the  layers 
sometimes  marked  with  ripples,  or  with  mud-cracks,  or  with 
the  tracks  of  the  animals  of  the  era ;  and  they  thus  show  that 
they  were  not  made  in  deep  water,  but,  instead,  that  they  were 
either  the  sea-beaches  or  the  off-shore  sand-flats  or  mud-deposits 
of  the  era ;  and  that  part  of  the  time  they  were  above  the  water's 
level,  exposed  to  the  drying  air  or  sun,  for  only  thus  can  mud- 
cracks  be  made. 

2.  As  the  era  advanced,  limestone  strata  (magnesian  lime- 
stones, mainly)  of  great  extent  were  formed  over  the  region  of 
the  Mississippi  Yalley,  or  the  Interior  region  of  the  continent, 
while  sandstones  and  shales  with  but  little  limestone  were  ac- 


LOWER  SILURIAN.  117 


cumulating  in  the  area  —  then  a  shallow  sea  —  now  occupied 
by  the  Appalachian  Mountains. 

3.  Next  a  limestone  —  the  Trenton  limestone  —  was  in  pro- 
gress over  both  the  Appalachian  region  from  the  Green  Moun- 
tains to  Alabama  and  the  Interior  region,  and  also  far  west  and 
north,  —  the  most  extensive  limestone  formation  in  the  world's 
history.     The  limestone  was  named  from  Trenton  Falls,  on  West 
Canada  Creek,  near  Utica,  New  York,  where  the  gorge  is  cut 
through  it.     It  includes  the  Galena  or  lead-bearing  limestone 
of  Illinois  and  Wisconsin. 

4.  Finally,    limestone-making    was    again    confined    almost 
wholly  to  the  Interior  region,  and  the  Appalachian  area,  in- 
cluding New  York  and  the  Green  Mountains   on  the  north, 
was  receiving  fragmental  deposits  for  sandstones,  shales,  and 
conglomerates. 

In  Great  Britain  there  are,  first,  slates  and  sandstones  of  great 
thickness  in  the  Longmynd  and  Wales,  overlaid  by  the  "  Lingula 
flags  "  (the  equivalent  of  the  Potsdam  sandstone) ;  above  these, 
other  slates  and  flags  (laminated  sandstones),  with  some  layers 
of  limestone,  including  the  Llandeilo  flags,  the  Bala  beds,  and 
the  Lower  Llandovery  in  South  Wales,  —  all  making  one  con- 
formable series. 

2.  Life. 

The  seas  abounded  in  life,  but  no  trace  of  anything  terres- 
trial has  yet  been  found. 

The  plants  found  are  aft  sea-weeds.     One  of  the  specimens 


118 


PALEOZOIC  TIME. 


is  represented  in  Pig.  92.  Some  thin  deposits  of  coal  occur 
in  one  of  the  formations,  which  are  supposed  to  have  come 
from  buried  sea-weeds,  or  else  from  animal  material. 

The  animals  are  all  Invertebrates ;  in  other  words,  no  trace 
of  a  Vertebrate,  not  even  of  the  lowest  of  Fishes,  has  yet  been 
discovered  among  the  animal  relics.  But  all  the  four  sub- 
kingdoms  of  Invertebrates  are  represented,  —  the  Protozoan, 
the  Eadiate,  the  Molluscan,  and  the  Articulate. 


Figs.  92,  93. 


Sea-weed.  —  Sponge. 
Fig.  92,  Buthotrephis  gracilis ;  93,  Archsepcyathus  Atlanticus. 

Protozoans,  —  Among  Protozoans  there  were  Rhizopods  and 
Sponges.  One  of  the  Sponges  is  represented  half  the  natural 
size  in  Pig.  93  a,  and  a  transverse  section  of  it,  natural  size, 
in  Pig.  93  b.  The  irregular  cellular  structure,  with  the  absence 
of  radiating  plates,  is  evidence  that  it  is  not  a  coral. 

Radiates.  —  The  Radiates  include  Corals,  Crinoids,  and  Star- 
fishes. Pig.  94  is  a  side-view  of  one  of  the  conical  corals  of 
the  Trenton  limestone;  the  top  is  a  cup,  radiated  with  plates, 
somewhat  like  Pig.  15,  page  29.  When  living,  the  flower-like 


LOWER  SILURIAN. 


119 


animal  had  no  doubt  its  beautiful  colors,  like  those  of  modern 
time,  and  its  aspect  may  be  quite  well  represented  by  Fig.  16, 
page  30. 

Figs.  94,  95. 


Polyp-Corals. 
Fig.  94,  Petraia  corniculum ;  95,  Columnaria  alveolata  ;  95  a,  top  view  of  same. 

Another  coral,  honeycomb-like  in  its  columnar  structure,  is 
represented  in  Fig.  95.  The  cells  are  radiated,  as  shown  in 
Fig.  95 ;  but  in  a  vertical  section  (as  seen  in  such  a  section  of 
one  of  the  cells  in  Fig.  95  a)  the  cells  are  crossed  by  horizon- 
tal partitions.  The  coral  has  been  found  in  masses  several 
feet  in  diameter. 

Figs.  96-99  represent  some  of  the  Crinoids  and  Star-fishes. 
Fig.  97  shows  one  of  the  Crinoids  of  the  Trenton  limestone, 
though  not  quite  a  perfect  one,  as  the  arms  are  broken  off  at 
the  tips,  and  the  stem  below  (by  which  it  was  attached  to  the 
rock  of-  the  sea-bottom,  and  which  may  have  been  three  or  four 
inches  long)  is  mostly  wanting.  The  name  Crinoid  means  lily-  \ 


like;  but  the  petals  or  rays  of  the  flower-like  animal  consist 
of  small  pieces  of  limestone  (the  secretion  of  the  animal)  fitting 
well  together.  Fig.  96  shows  the  form  of  another  kind  of 
Crinoid,  —  one  of  very  irregular  shape;  its  stem  when  living 


120 


PALEOZOIC  TIME. 


was  run  down  into  the  mud  of  the  sea-bottom,  instead  of  being 
attached  to  a  rock.  Figs.  98,  99  are  two  of  the  Star-fishes  of 
the  ancient  seas,  related  to  the  modern  Ophiurans. 

Figs.  96-99. 


Fig.  100. 


Asterioids.  -  Crinoids. 

Fig.  96,  Pleurocystis  filitextus ;  97,  Lecanocrinus  elegans  —  Crinoids  :  Fig.  98,  Palaeaster  matutina ; 
99,  Taeniaster  spinosa. 

Mollusks.  —  The  Mollusks  were  of  various  kinds,  all  the 
principal  grand  divisions  of  the  class  having  been  represented 
by  species.  Par  the  most  abundant  were  what  are  called  Brachi- 
opods,  a  group  that  has  comparatively  few  kinds 
in  modern  seas.  One  of  the  earliest  Brachiopods 
from  the  Potsdam  sandstone  had  a  shell  not  larger 
than  a  finger-nail;  a  large  specimen  of  it  is  rep- 
resented in  Fig.  100.  It  is  called  a  Lingnla  (or 
Lingulella) ,  from  the  Latin  lingua,  a  tongue,  in  allusion  to 
the  tongue-like  shape  of  some  species.  A  related  species  is 
found  in  the  Lingula  flags  of  Great  Britain.  "When  living 


LOWER  SILURIAN. 


121 


it  was  fixed  to  the  sea-bottom  by  a  fleshy  stem  proceeding 
downward  from  the  pointed  end  or  beak  of  the  shell,  and 
passing  into  the  mud  or  sand;  and  as  the  shells  are  often  in 
great  numbers  together,  they  must  have  grown  thickly  over 
the  sandy  or  muddy  surface. 

Other  common  Brachiopods  from  the  Trenton  limestone  are 
represented  in  Figs.  101  to  104. 


Figs.  101-104. 

102. 


Fig.  105. 


Brachiopods. 
Fig.  101,  Leptaena  sericea ;  102,  Orthis  occidentalis ;  103,  O.  lynx ;  104,  O.  testudinaria. 

The  shells  have  two  valves  like  those  of  a  clam  or  oyster; 
but  they  are  unlike  common  Bivalves  in  their  symmetrical 
form;  a  line  let  fall  from  the  beak  divides 
them  into  equal  halves,  whereas  in  a  Clam, 
as  shown  in  Fig.  105,  such  a  line  divides 
the  shell  very  unequally.  Moreover,  the 
mouth  in  a  Brachiopod  is  at  the  middle 
of  the  shell,  whereas  in  common  Bivalves  it  is  toward  one 
end  (near  a,  in  Fig.  105) ;  and  further,  one  valve  is  the 
upper  and  the  other  the  lower,  while  in  a  Clam,  and  related 
kinds,  one  is  the  right  and  the  other  the  left.  Thus  the 

6 


122  PALEOZOIC  TIME. 


animal   in  this  ancient   group  called   Brachiopods  has  a  posi- 
tion in  its  shell  just  transverse  to  that  of  a  Clam.     The  ani- 
mal is  also  peculiar  in  having  two  spiral  fringed  arms,  and  to 
FI    ice  ^is   the  name,  from  the  Greek  for  arm-foot, 

alludes.  Fig.  106  shows  these  arms  in  a 
modern  species ;  one  of  the  pair  is  rolled  up 
spirally  in  its  ordinary  position,  while  the. 
other  is  thrown  out.  The  animal  has  no 
gills  or  branchiae.  The  Trenton  limestone 
was  made  largely  of  the  shells  of  Brachio- 

Khynchonella  psittacea.      ^    Crmoids    and    Corals    havmg    contributed 

little  toward  it. 

The  Clam  and  Oyster  and  other  ordinary  Bivalves  have  a 
thin  fold  of  the  skin  lying  like  a  mantle  over  the  body 
against  the  shell ;  then,  inside  of  the  mantle  and  either  side 
of  the  body,  thin  leaf-like  gills  or  branchiae ;  and  then  the 
body  with  no  arm-like  appendages.  In  allusion  to  the  thin 
lamellar  branchiae,  they  are  called  LamellibrancJis.  There  were 
some  Lamellibranchs  in  the  Lower  Silurian,  but  they  were 
few  compared  with  the  Brachiopods.  Fig.  107  represents  one 
of  them,  related  to  the  Mussel  of  modern  sea-shores. 

There  were  also  some  spiral  shells,  two  of  them  of  the 
forms  shown  in  Figs.  108,  109.  They  belong  to  the  tribe 
of  Gasteropods,  so  called  because  the  animal  crawls  on  its 
ventral  surface.  The  ordinary  spiral  marine  shells,  and  also 
the  common  snail,  are  of  this  tribe.  The  snail  may  be  often 


LOWER  SILURIAN. 


123 


Figs.  107  - 109. 


seen   crawling   thus   with    its    shell    over    its    back;   and    the 
marine   species   when  living,  if  put  into  a  jar  of  salt  water, 
will    soon    be    found  in 
motion  over  the  glass. 

There  were  also  many 
species  of  the  highest  di- 
vision of  Mollusks,  — 
those  related  to  the  Nau- 
tilus, and  called  Cephal- 
j  because  the  animal 


Fig.  110. 


Mollusks. 

haS      the      head      furnished       Fig.  I07>  Avicula  Trentonensis  ;  108,  Murchisonia  bicincta ; 

109,  Pleurotomana  lenticularis. 

with  stout  arms  for  cling- 
ing; from  the  Greek  for  head  and  feet.     A  modern  Nautilus, 
with  the  animal  in  its  shell,  is  represented  in  Fig.  110.     The 

shell  has  transverse  partitions,  or 
is  chambered,  and  in  this  differs 
from  the  shell  of  the  Snail  and 
all  Gasteropods.  The  animal  oc- 
cupies the  large  outer  chamber, 
and  is  peculiar  in  having  large 
eyes  like  a  fish,  and  a  series 
of  stout  arms  around  the  mouth 
provided  with  suckers  for  cling- 
ing. A  different  kind  of  Cephalopod,  from  modern  seas,  is 
represented  in  Pig.  Ill,  —  a  kind  having  no  external  shell, 
but  instead  a  thin  internal  bone  (Pig.  Ill  jo),  but  with 


Modern  Cephalopod. 
Nautilus  (X  #). 


124 


PALEOZOIC  TIME. 


large  eyes  and  a  series  of  arms  around  the  mouth,  as  in 
the  Nautilus.  In  the  Lower  Silurian  era  there  were  spe- 
cies of  Nautilus,  but  quite  different  ones  from  those  of  later 


Fig.  111. 


Modern  Cepbalopod. 

The  Caiamary  or  Squid,  Loligo  vulgaris  (length  of  body,  6  to  12  inches) ;  *',  the  duct  by  which  the  ink  is 
thrown  out;  f,  the  "pen." 


time.  But  the  earliest  Silurian  species  of  Cephalopods  and 
the  largest  had  straight  shells,  like  that  of  a  Nautilus  straight- 
ened out,  —  whence  the  name  Orthoceras,  meaning  a  straight 
horn.  One  of  them,  from  the  Trenton  limestone,  is  represented 
in  Pig.  112 ;  it  has  partitions  like  the  shell  of  the  Nautilus. 

Fig.  112. 


Cephalopod. 
Orthoceras  junceum. 


In  both  the  Nautilus  and  the  Orthoceras  a  tube  (called  the 
siphuncle,  meaning  little  siphon)  passes  from  the  outer  cham- 
ber through  the  partitions  and  all  the  chambers  ;  and  the 
hole  in  one  of  the  partitions  is  shown  in  Pig.  112  a.  Some 


LOWER  SILURIAN. 


125 


of  the  shells  of  species  of  Orthoceras  from  the  Trenton  lime- 
stone are  as  large  round  as  a  flour-barrel,  and  must  have  been 
from  twelve  to  fifteen  feet  long. 

Another  kind  of  Mollusk,  of  quite  minute  size,  makes  cor- 
als. The  animals  look  like  polyps  externally,  as  shown  in 
Fig.  113,  which  represents  them  enlarged,  projecting  out  of 
their  cells.  Fig.  114  is 
a  view  of  one  of  the  deli- 
cate Lower  Silurian  cor- 
als, and  the  dots  show 
the  positions  of  the  little 
cells  of  the  animal.  The 


Figs.  113,  114. 


Bryozoans. 


-  p.^  ii3   Eschara>  snowing  aniinals  extended  out  of  their  cells 

(  X  8)  ;  113  a,  one  of  the  animals  removed  from  its  cell  more  en- 

-  larged;  114,   Ptilodictya  fenestrata,  a  Lower  Silurian  species, 
natural  size  ;  114  a,  portion  of  surface  of  same  enlarged. 


are     CalleCl 
meaning 

ma  Is,  the  name  alluding 

to  the  corals,  which  are  sometimes  moss-like  in  delicacy  and 
form.  Although  so  small,  these  corals  are  a  prominent  con- 
stituent of  some  of  the  Silurian  limestones. 

Articulates.  —  The  Lower  Silurian  Articulates  that  have  been 
made  out  are  either  Worms  or  Crustaceans  ;  no  Insects  or  Spi- 
ders having  been  present,  since  these  are  terrestrial  species. 
The  most  remarkable  of  the  Crustaceans,  and  the  highest  spe- 
cies of  the  world  at  the  commencement  of  Lower  Silurian  time, 
and  later  in  this  era  second  only  to  the  Orthocerata,  were  the 
Trilobites,  —  so  named  because  the  body  has  three  lobes  or 
divisions  longitudinally,  as  shown  in  Figs.  115  to  117.  One 


126 


PALEOZOIC  TIME. 


of  the  very  earliest  species  is  represented  in  Pig.  115;  it  was 
a  gigantic  species,  the  figure  being  only  one  third  the  natural 
length.  It  has  some  resemblance  to  a  lobster,  and  yet  is  very 
different.  The  position  of  the  large  eyes  is  apparent  on  the 


Figs.  115-118. 


Trilobitcs. 

Fig.  115,  Paradoxides  Harlani  (X  }4);  116,  Asaphus  gigas  (X  #) ;  117,  Calymene  Blumenbachii  j  118.  same 
rolled  up,  as  it  is  often  found. 

head  shield.  Two  other  species,  from  the  Trenton,  are  repre- 
sented in  Pigs.  116,  117.  The  latter  is  shown  folded  up  in 
Pig.  118,  a  common  condition  of  the  specimens.  The  forms 
of  three  modern  species  of  Crustaceans  having  some  resem- 


LOWER  SILURIAN.  127 


blance  to  the  ancient  Trilobites  are  shown  in  Pigs.  119  to  122. 
Figs.  121,  122  are  female  and  male  of  the  same  species.  But 
the  Trilobites  differed  from 

Figs.  119-122. 

all  these  in  having  had  no 
true  legs.  They  are  supposed 
to  have  had  only  thin  fleshy 
plates,  for  swimming. 

The   earliest    life    of    the 

Modern  Crustaceans. 

Lower    Silurian    was    made  Fig.119(aspeciesof  Serolis(x  ^);  I2o  spedesof  Porcel. 

,  .  />/-<••  i  lio  '  181»  I22«  female  and  male  o{  Sapphirina  iris. 

up      largely      or     urinoiqs, 

Brachiopods,  Worms,  and  Trilobites.  It  was  almost  all  sta- 
tionary life;  that  is,  the  most  of  the  species  were  attached  to 
the  sea-bottom  by  stems.  Such  were  all  the  Crinoids  and 
Brachiopods.  Trilobites  swam  free;  but,  having  only  swim- 
ming legs,  they  probably  often  attached  themselves  to  the  rocks, 
like  the  shells  called  Limpets.  Afterward  there  were  Mussel- 
like  shells  and  corals,  which  were  also  attached  species,  —  Mus- 
sels living  attached  to  rocks  by  a  byssus  or  horny  threads. 
Besides  these  there  were  the  locomotive  species,  Gasteropods 
and  Orthocerata;  the  latter  may  have  given  much  activity  to 
the  seas,  for  Cephalopods  are  not  snail-like  in  pace,  like  all 
Gasteropods,  but  fleet  movers,  like  fishes.  Yet  these  ancient 
species,  with  their  long  unwieldy  shells,  must  have  been  slow  \ 
compared  with  the  Cephalopods  of  later  time. 

The  life  of  the  Lower  Silurian  changed  much  in  species  dur- 
ing its  progress.     The  era  has  been  divided  into  three  periods : 


128  PALEOZOIC  TIME. 


no  animals  of  the  earlier  part  of  the  first  of  these  periods  — 
/  the  Primordial  —  existed  in  the  second,  and  none  of  the 

earlier  part  of  the  second  existed  in  the  third.  Moreover, 
;  species  were  disappearing  and  others  appearing  through  each 

of  the  successive  periods. 

3.  Mountain-making. 

The  close  of  the  Lower  Silurian  was  a  time  of  upturning 
and  mountain-making  in  North  America,  Great  Britain,  and 
I  Europe.  The  Green  Mountains,  from  Canada  to  southern  Con- 
necticut, and  perhaps  other  heights  to  the  southwest,  were 
then  made.  The  rocks  —  which  include  a  great  limestone  for- 
mation (the  upper  part  of  which  is  referred  to  the  Trenton) 
and  also  various  fragmental  rocks  overlying  the  limestone  — 
were  folded  and  crystallized  by  the  heat  produced  by  the  dis- 
turbance added  to  that  from  the  earth's  depths,  and  were  thus 
changed  at  the  time  to  metamorphic  rocks :  the  fossiliferous 
limestone,  to  white  and  clouded  crystalline  or  architectural  mar- 
ble, —  of  which  Canaan  in  Connecticut,  Lee  in  Massachusetts, 
and  Eutland  in  Vermont  afford  noted  examples;  the  quartzose 
sand-beds,  to  quartzyte;  the  mud-beds,  to  gneiss,  mica  schist, 
and  other  crystalline  rocks. 

In  Great  Britain  the  Lower  Silurian  formations,  which  are 
throughout  conformable,  are  upturned  so  as  to  lie  unconform- 
ably  beneath  the  beds  of  the  next  era,  —  the  Upper  Silurian. 
The  elevation  of  the  Westmoreland  Hills,  of  the  mountains  in 


UPPER  SILURIAN.  129 


North  Wales,  and  of  the  range  of  Southern  Scotland  from  St. 
AbVs  Head,  on  the  east  coast,  to  the  Mull  of  Galloway,  has 
been  referred  to  this  era. 

The  maximum  thickness   of  the  Lower   Silurian  rocks   of  > 
Britain  has  been  stated  to  be  over  40,000  feet.     In  the  Green  - 
Mountain  region  it  was  probably  not  less  than  20,000  feet;  in 
Pennsylvania,  about   11,000  feet;   in   Illinois,  about  800;   in 
Missouri,  nearly  2,200  feet. 

2.  Upper  Silurian  Era. 
1.  Bocks, 

The  rocks  of  the  Upper  Silurian  also  are  sandstones,  con- 
glomerates, shales,  and  limestones. 

1.  There  was  first  in  progress,  during  what  has  been  called 
the  Niagara  period,  the  formation  which  includes  the  Niagara 
limestone,  —  which,  like  the  Trenton  limestone,  was  one  of  the 
great  limestone  formations  of  ancient  time.  In  Western  New 
York  and  to  the  southwest  along  the  Appalachian  region  — 
still  a  part  of  the  continental  sea  —  the  earlier  beds  forming 
were  a  series  of  sandstone  strata  (the  Medina  sandstone),  some- 
what pebbly  below  and  argillaceous  above;  then  other  argil- 
laceous sandstones,  and  in  them  a  bed  of  red  iron  ore,  with  a 
little  limestone  in  the  upper  part;  then  the  Niagara  shale  and 
limestone,  the  strata  at  Niagara  Palls,  where  the  upper  80  feet 
are  limestone  and  the  lower  80  feet  shale.  To  the  west  of 
New  York,  the  Niagara  shale  formation  is  of  little  extent, 
6*  i 


1:30  PALEOZOIC  TIME. 


while  the   limestone   spreads  very  widely,  reaching   into  Iowa 
and  Tennessee. 
/      The  layers  of  the  Medina  sandstone  often  have  ripple-marks, 

';  mud-cracks,  wave-marks,  and  other   evidences  of  mud-flat   or 

7 

^  sand-flat  origin,  showing  that  Central  and  Western  New  York, 

with  the  region  to  the  southwest,  was  then  an  area  of  great 
sand-flats  over  an  interior  sea;  but  later  this  interior  sea  was 
more  open  and  clearer;  so  that  there  was  less  sediment,  and 
the  life  required  for  making  limestones  flourished. 

In  Great  Britain  the  Wenlock  shale  and  limestone  are  of 
the  age  of  the  Niagara  shale  and  limestone.  They  are  in 
view  between  Aymestry  and  Ludlow,  near  Dudley,  and  else- 
where. The  limestone,  like  the  Niagara,  is  full  of  fossils. 

2.  Afterward  the  Salina  formation,  noted  for  its  salt,  was 
made.     Its  clayey  rocks  and  salt  show  that  Central  New  York, 
the  borders  of  Canada  to  the  west,  and  part  of  Michigan  were 
then  the  site  of  a  great  salt  basin,  where  sea-water  evaporated, 
impregnating  the  mud  of  the  shallow  sea  with  salt,  or  making 
deposits  of  rock-salt.     The  brines  of  Salina  and  that  vicinity 

I  [  in  New  York  are  salt-water  wells,  obtained  by  boring  down 
to  this  saliferous  rock;  and  at  Goderich  in  Canada  there  is 
a  bed  of  rock-salt  14  to  40  feet  thick.  Other  salt-bearing 

/        rocks  were  made  at  the  same  time  in  Virginia. 

3.  Next  followed  another  limestone  formation  of  less  extent 
than  the  Niagara,  called  the  Lower  Helderberg,  from  the  Hel- 
derberg  Mountains  southwest  of  Albany,  where  it  occurs.     It 


UPPER  SILURIAN.  131 


extends  southwestward  along  the  Appalachians;  also  through 
parts  of  the  Mississippi  Valley  where  it  rests  directly  on  the 
Niagara  limestone.  It  also  occnrs  at  some  points  in  the  Con- 
necticut Yalley.  A  sandstone  —  the  Oriskany  sandstone  — 
overlies  it  in  Central  New  York  and  along  the  Appalachian 
region,  and  in  some  places  to  the  west,  from  Ohio  to  Missouri. 
Following  the  "Wenlock  group  in  Great  Britain  there  is 
the  Ludlow  group,  consisting  of  sandstones,  shales,  and  the 
Aymestry  limestone,  corresponding  in  age  with  the  later  part 
of  the  American  Upper  Silurian. 

2.  Life. 

1,  Plants.  —  As  in  the  Lower  Silurian,  sea- weeds  were  abun- 
dant; but  before  the  close  of  the  era  there  were  also  terrestrial  j 
plants.     The  species  were  not  Mosses  of  the  lower  division  of 
Cryptogams,  or  flowerless  plants,  and  not  Grasses,  but  species  of 
the  Ground-Pine  tribe,  or  Lycopods,  —  a  section  of  the  highest) 
Cryptogams.     They  are  described  beyond,  in  the  account  of  the 
Devonian  plants.     It  cannot  be   affirmed  that  there  were  no 
Lichens  or  Fungi  over  the  Silurian  rocky  lands,  or  those  of 
earlier  time ;  for  such  terrestrial  species,  if  existing,  would  not 
have  become  fossilized,  since  the  rocks  are  mainly  of  marine  or 
marsh  origin.     But  that  there  were  no  Mosses  may  be  safely 
inferred  from  the  absence  of  all  fossil  Mosses  from  the  rocks) 
of  the  following  Devonian  and  Carboniferous  ages. 

2,  Animals.  —  The  animals  included  species  of  all  the  grand 


132 


PALEOZOIC  TIME. 


divisions  existing  in  the  Lower  Silurian,  Protozoans,  Radiates, 
Mollusks,  and  Articulates,  with  the  same  great  preponderance 
of  Brachiopods  among  Mollusks,  and  Trilobites  among  Articu- 
lates. In  addition,  before  the  close  of  the  era,  there  were 
Eishes  in  the  seas,  the  earliest  of  Vertebrates.  No  remains  of 
terrestrial  animal  life  have  yet  been  found. 

A  few  figures  of  the  Invertebrates  are  here  given.      Pigs. 
123,  124  represent  two  of  the  corals  of  the  Niagara  period; 


Figs.  123-125. 


Polyp-Corals.  —  Crinoid. 
Fig.  123,  Zaphrentis  bilateralis;  124,  Halysites  catenulata.  — Crinoid  :  Fig.  125,  Stephanocrinus  angulatus. 

Eig.  123  related  to  the  coral  of  the  Lower  Silurian,  figured 
on  page  119;  Eig.  124,  a  coral  imbedded  in  limestone,  which 
looks,  in  a  section  of  the  limestone,  a  little  like  a  chain,  or  a 
string  of  links,  and  has  hence  been  called  Chain-coral.  Eig. 
125  shows  the  form  of  one  of  the  Niagara  Crinoids. 

Some   of   the  more   common   Bracniopods   of   the    Niagara 
group  are  represented  in  Eigs.  126-128. 


UPPER  SILURIAN. 


133 


Figs.  126-128. 


127 


BracMopods. 

Fig.  126,  Strophomena  rhomboidalis ;  127,  side-view  of  Spirifer  Niagarensis ;  128,  Orthis  bilobus  ;  128  a, 
enlarged  view  of  same. 

The  following  are  figures  of  two  of  the  larger  Trilobites. 
Both  figures  are  reduced  views,  Eig.  129  being  but  one  third 
the  natural  length,  and  Fig.  130  one  fourth. 

Figs.  129,  130. 


Trilobites. 
Fig.  129.  LichasBoltoni(X  tf);  130,  Homalonotusdelphinocephalus(X  ja 

The  fishes  were  related  to  the  modern  Sharks  and  Gars. 
Descriptions  of  the  kinds  are  given  under  the  Devonian,  the 
specimens  of  Devonian  rocks  being  more  perfect  and  afford- 
ing better  illustrations  of  the  subject. 


134  PALEOZOIC  TIME. 


3.    Observations  on  the  Silurian  Age. 

1.  The  distribution  of  the  emerged  lands  of  North  America 
at  the  close  of  Archaean  time  led  us  to  the  conclusion   (page 
108)  that  the  continent  was  then  already  denned  in  area,  and 
its  plan  of  future  progress  made  manifest.     The  facts  respect- 
ing the  Silurian  rocks   sustain  this  view,   and  show   how  the 
work  of  completing  the  continent  went  on  through  the  Silu- 
rian  era.     It  has  already  been  explained,  by  reference  to  the 
map  of  the  Archaean  dry  land,  on  the  same  page,  that  rock- 
making,  and  therefore  progress,  was  confined  to  the  submerged 
part   of  the  continent.      The  map  shows  the  position   of  the 
coast-line  along  which  the  waves  broke  when  the  Silurian  age 
began,  making  the  sea-beach  deposits  and  sand-flats  that  now 
form  part  of  the  Potsdam  sandstone.     The  Appalachian  region 
must  have  been  one  of  the  areas  of   great  sand-flats  or  reefs, 
for  its  eastern  side  was  the   course   of  a   range   of   Archaean 
mountains ;    and    the   Rocky    Mountain   region,   for  the   same 
reason,  was  probably  another  of  the  shallower  portions  of  the 
continent.     The  Lower  Silurian  continental  sea  had  its  great- 
est depth  over  the  intermediate  Interior  region,  of  which  the 
present  Gulf  of  Mexico  was  then  the  southern  part.     These  in- 
ferences are  sustained  by  the  whole  course  of  the  history. 

2.  With  the  progress  of  the   Silurian  the  dry  land  of  the 
north  received   a   gradual   extension  southward,  southeastward, 
and  southwestward.     This  was  the  direction  of  growth.     Shore- 


SILURIAN  AGE.  135 


lines  of  the  successive  periods  were  more  and  more  remote 
from  the  old  Archaean  sea-shore,  for  the  limits  of  the  suc- 
cessive formations  are  farther  and  farther  south;  so  that,  at 
the  close  of  the  age,  the  coast-line  in  the  region  of  the  mod- 
ern State  of  New  York  probably  lay  a  little  to  the  south  of 
the  present  Mohawk  valley,  and,  extending  westward  from 
Niagara  over  Western  Canada,  it  bent  northward  around  Lake 
Huron ;  thence  it  turned  southward  so  as  to  cross  Northern 
Illinois  before  taking  its  course  to  the  far  north  parallel  with 
the  west  side  of  the  Archaean  nucleus.  These  conclusions  are 
deduced  from  the  limits  of  the  Silurian  formations,  shown 
on  the  map  on  page  105. 

3.  At  the  close  of  the  Lower  Silurian  the  Green  Mountains 
were  made  by  an  upturning  and  crystallization  of  the  rocks. 
A  new  area  of  dry  land  was  thus  formed  between  the  seas  of 
New  York  and  New  England,  and  the  valley  of  Lake  Cham- 
plain  was  a  consequence  of  the  uplifting.  There  was  also  an 
upward  bending  of  the  earth's  crust,  but  without  upturning, 
over  an  area  from  Lake  Erie  across  the  Cincinnati  region 
to  Tennessee,  making  another  spot  of  dry  land.  The  Green" 
Mountains  were  raised  parallel  to  the  neighboring  Archaean 
Adirondacks ;  the  Cincinnati  uplift  was  parallel  nearly  to  the 
Archaean  Blue  Eidge.  Thus  progress  was  strictly  after  the 
plan  laid  down  in  Archaean  time. 

Southern  and  Western  New  York,  and  the  region  of  the 
Alleghany  Mountains,  remained  within  the  limits  of  the  con- 
tinental sea  through  the  Silurian  age. 


136  PALEOZOIC  TIME. 


4.  The  rocks  of  the  Interior  region  of  the  continent  (now 
the  great  Mississippi  valley)  were  mainly  limestones  from  the 
beginning  of  the  Silurian  to  its  close;  while  those  of  the 
Appalachian  region  were  mainly  sandstones,  conglomerates,  and 
s/iales.  The  Trenton  limestone  spread  over  both;  but,  in 
general,  there  were  fragmental  deposits  forming  over  the  Ap- 
palachian region  at  the  same  time  that  there  were  limestone 
deposits  in  progress  to  the  west  of  it.  The  Trenton  lime- 
stone is  an  exception;  but  before  the  Trenton  period  closed 
the  Interior  region  was  alone  in  limestone-making,  the  Appa- 
lachian having  become  again,  as  the  rocks  show,  an  area  of 
mud-flats  and  sand-flats. 

These  facts  prove  that  the  Appalachian  region  was  a  great 
reef  region  through  the  era,  and  that  over  the  interior  of  the 
continent  there  was  at  the  same  time  a  clear  and  wide  sea,  one 
seldom  swept  by  sediment-bearing  currents.  The  limestones 
were  made  of  shells,  crinoids,  and  corals  mostly  ground  up; 
and  their  freedom  in  general  from  much  impurity  shows  that 
the  marine  life  had  there  the  pure  waters  in  which  it  best 
thrives. 

Several  of  the  sandstones  and  shales  contain  ripple-marks, 
mud-cracks,  or  foot-prints,  proving  that  they  were  made,  not 
in  a  deep  sea,  but  in  shallow  waters,  and  that  the  deposits 
were  sometimes  exposed  above  the  water's  surface. 

C5.  Over  10,000  species  of  fossils  were  described  from  Lower 
and  Upper  Silurian  rocks  up  to  the  year  1872.  The  species 


DEVONIAN  AGE.  137 


continued  to  change  through  the  Upper  Silurian  era  as  well 
as  the  Lower  Silurian;  that  is,  the  species  of  the  early  part 
had  nearly  all  disappeared  and  new  species  had  become  sub- 
stituted before  the  later  part  of  the  era  began;  and  each  of 
the  successive  subdivisions  in  the  rocks  indicates  some  old  fea- 
ture lost  during  its  progress  or  in  the  transition,  and  some 
new  feature  gained. 

2.    Devonian  Age,  or  Age  of  Fishes. 

The  term  Devonian  was  first  applied  to  the  rocks  of  the 
age  in  Great  Britain  by  Sedgwick  and  Murchison,  and  al- 
ludes to  the  region  of  South  Devon,  where  the  rocks  occur 
and  abound  in  fossils. 

Through  the  age  the  land  had  its  plants  and  insects,  and 
the  seas  their  numerous  fishes,  besides  species  of  all  the  lower 
orders  of  life.  The  regions  of  Devonian  rocks  are  those  ver- 
tically lined  on  the  North  American  map,  page  105,  and  the 
map  of  England,  page  114. 

1.    Rocks. 

The  Lower  Devonian  rocks  of  North  America  overlie  con- 
formably the  Upper  Silurian,  making  a  continuous  series  with 
them. 

The  age  commenced  with  the  era  of  the  Corniferous  lime- 
stone. This  was  the  great  limestone  of  the  Devonian,  just  as 
the  Niagara  was  of  the  Upper  Silurian,  and  the  Trenton  lime- 


138  PALEOZOIC  TIME. 


stone  of  the  Lower  Silurian.  It  spreads  through  New  York 
from  the  Helderberg  Mountains  south  of  Albany,  where  it  has 
been  called  the  Upper  Helderberg  limestone;  and  stretches 
westward  to  the  Mississippi,  and  beyond  it  into  Iowa  and 
Missouri.  In  New  York  and  along  the  Appalachian  region, 
it  is  underlaid  by  a  sandstone  or  grit  rock. 

The  limestone  is  in  some  places  a  coral-reef  rock,  as  plainly 
so  as  any  coral-reef  limestone  in  modern  tropical  seas.  Near 
Louisville,  Kentucky,  at  the  Ealls  of  the  Ohio,  it  consists  of 
an  aggregation  of  corals,  many  of  large  size,  and  some  are 
standing  in  the  position  of  growth.  The  limestone  rock  often 
contains  a  kind  of  flint  called  hornstone;  and,  as  the  Latin 
for  horn  is  cornu,  the  limestone  was  named  the  Corniferous 
limestone. 

The  Devonian  deposits  following  this  limestone  —  called 
often  the  Upper  Devonian  —  are  mostly  sandstones  and  shales, 
named  the  Hamilton,  Portage,  and  Chemuug  beds,  from  locali- 
ties in  New  York ;  and  above  these,  at  the  top,  there  is  an 
extensive  conglomerate  and  sandstone  called  the  Catskill  group. 
These  fragmental  formations  are  confined  mainly  to  Southern 
New  York  and  to  the  Appalachian  region  to  the  southwest. 

In  parts  of  the  Interior  region  there  were  limestones  form- 
ing when  the  Hamilton  sandstones  and  shales  were  in  pro- 
gress; but  subsequent  to  these  limestones  the  Devonian  rock 
formed  in  the  Interior  region  is  mainly  a  shale  of  little 
thickness. 


DEVONIAN  AGE.  139 


The  flagging-stone  so  much  used  in  New  York  and  the 
adjoining  States  is  an  argillaceous  sandstone  from  the  Hamil- 
ton beds  at  Kingston  and  other  places  on  the  Hudson  Eiver. 

In  Great  Britain  the  Devonian  formation  includes  a  great 
thickness  of  red  sandstone  in  Scotland,  Wales,  and  England, 
which  was  formerly  distinguished  as  the  "  Old  Red  Sandstone/'' 
In  South  Devon  there  are  limestone  and  shales  in  place  of 
red  sandstone,  and  hence  a  greater  abundance  of  fossils.  In 
the  Eifel,  Germany,  the  Eifel  limestone  is  a  Devonian  coral- 
reef  rock  of  the  age  of  the  Corniferous.  Devonian  sandstones 
cover  a  large  area  in  Eussia. 

2.    Life. 

1,  Plants.  —  The  plants  included,  besides  sea-weeds,  various 
terrestrial  kinds;   and  among  them,  in  the  middle  and   later 
Devonian,  large  forest-trees. 

These  early  species,  as  stated  on  page  131,  were  mostly  of 
the  higher  Cryptogams. 

7.  Ferns,  some  of  them  Tree-ferns.  A  portion  of  one  of 
the  Ferns  is  shown  in  Fig.  131,  and  part  of  the  stem  of  a 
Tree-fern  in  Fig.  132. 

2.  Equiseta.  —  The  modern  Equiseta,  or  Horse-tails  (the  lat- 
ter  term    a   translation   of   the   former)    have   striated  jointed 
stems,   which  may   be  pulled   or   broken  apart  easily  at  the 
articulations.     The    ancient    species    had    a    similar   character. 
A    portion    of    one    of    these    rush-like    Devonian    plants    is 


PALEOZOIC  TIME. 


Figs.  181,  132. 


Ferns. 


Hf.  .31.  NeuropKris  ^lymorph,  j  ,y,  TreeJim,  Caulopteris  aMiqua. 

represented  in  Fig.  133.  One  of  the  articulations  of  the  stem 
is  shown  at  a  b.  In  allusion  to  its  reed-like  character  it  is 
called  a  Odamit*,  from  the  Latin  calamm,  a  reed  The 
plant  represented  in  Fig.  134  is  supposed  by  some  to  belong 
the  Equ]Setum  tribe ;  the  word  AteroilKto  means  star-leaf. 


134 


133 


Fig.  133,  Calamites  transitionis  ;  134,  Asterophyllites  latifolia. 


DEVONIAN  AGE. 


141 


8.  Lycopods. — The  earliest  land  plants,  and  those  most  char- 
acteristic of  the  world  in  ancient  time,  were  the  Lycopods. 
The  little  trailing  Ground-Pines  of  our  modern  woods,  so 
much  used  for  decorating  churches  at  Christmas-time,  are 
examples  of  Ground-Pines;  the  close  resemblance  to  miniature 
Pine-trees  is  the  origin  of  this  name.  The  earliest  of  the  an- 
cient Lycopods  were  of  small  size,  but  some  of  those  of  the 
Middle  Devonian  were  large  forest- trees.  Fig.  135  represents 

Figs.  135  - 137. 


Lycopods.  —  Gymnosperms. 
F'g-  I3S>  Lepidodendron  primaevum  ;  136,  Sigillaria  Hallii.  —  Gymnosperm  :  137,  Cordaites  RobbiL 

a  part  of  the  exterior  of  one  of  the  Devonian  Lycopods. 
The  plants  are  called  Lepidodendrids  (from  the  Greek  for 
scale  and  tree) ,  in  allusion  to  a  resemblance  between  the  scarred 
surface  and  the  scaly  exterior  of  a  reptile.  The  scars  are  the 
bases  of  the  fallen  leaves,  and  resemble  the  same  on  a  dried 
branch  from  a  spruce-tree.  In  the  true  Lepidodendrids  the 
scars  are  in  alternate  order,  as  illustrated  in  Fig.  135.  In 


142  PALEOZOIC  TIME. 


another  group,  called  Sigillarifo,  the  scars  are  in  vertical  series, 
as  in  Fig.  136. 

4.  Phenogams,  or  Flowering  Plants.  —  Among  the  Flowering 
plants  there  were  trees  allied  to  the  Yew,  Spruce,  and  Pine, 
kinds  having  the  simplest  of  flowers,  and  the  seed  naked  in- 
stead of  in  pods.  In  allusion  to  the  latter  character  they  are 
called  Gymnosperms,  meaning  having  naked  seeds.  The  flowers 
and  fruit  are  usually  in  cone-like  groups,  and  in  allusion  to 
the  cones  a  large  part  of  the  species  are  Conifers.  Fig.  137 
is  probably  a  leaf  of  one  of  the  Conifers. 

2.  Animals.  —  Protozoans,  Radiates,  Mollusks,  and  Articu- 
lates were  represented  by  numerous  species,  as  in  the  Silurian 
age;  and  among  these  Brachiopods  were  the  prevailing  Mol- 
lusks, Corals  the  most  abundant  Eadiates,  and  Trilobites  the 
most  common  of  Articulates.  Three  of  the  Corals  of  the 
coral-reef  limestone  (Corniferous  limestone)  from  the  Falls  of 
the  Ohio,  near  Louisville,  are  represented  in  Figs.  138-140. 
Fig.  138  represents  a  specimen  of  one  of  the  large  simple 
Corals,  broken  at  both  extremities.  The  radiating  plates  are 
seen  at  top.  The  top,  when  perfect,  had  a  depression  rayed 
with  such  plates,  and  to  this  the  name  of  this  ancient  group 
of  Corals,  Cyathophylloid*,  alludes,  it  coming  from  the  Greek 
for  cup  and  leaf.  Some  specimens  of  the  species  are  nearly 
three  inches  in  diameter  at  top  and  a  foot  long;  and,  when 
living,  the  polyp  or  flower-animal  when  expanded  was  as  large 
as  a  small-sized  sunflower,  and  probably  as  brilliant  in  color. 


DEVONIAN  AGE. 


143 


Fig.  139  shows  the  surface  of  a  massive  coral  whose  polyps 
covered  the  surface  like  those  of  Fig.  14,  on  page  29.  The 
other  kind,  Fig.  140,  is  one  of  the  most  common ;  the  structure 

Figs.  138 -UO. 

i£Hfcfilfeife*»i 

138 


Polyp-Corals. 
Fig.  138,  Zaphrantis  gigantea  ;  139,  Phillipsastrsea  Verneuili ;  140,  Favosites  Goldfussi. 

is   columnar,  suggesting  that  of  a  honeycomb,  and  hence  its 
name,  Favosites,  from  the  Latin  favus,  a  honeycomfi. 

Besides  marine  species  there  were  also  Insects  among  ter- 
restrial Articulates.  Fig.  141  represents  a  wing  of  one  of 
the  May-flies  of  the  Devonian  world ;  a  gigantic  species  much 
exceeding  any  now  known.  It  measured  five  inches  in  spread 


144 


PALEOZOIC  TIME. 


Fig.  141. 


of  wings.  The  May-flies  or  Ephemerae  are  species  that  live 
in  the  water  during  the  young  or  larval  state,  and  when  ma- 
ture fly  in  clouds  over  moist 
places.  One  of  the  Devonian 
kinds  could  make  the  shrill 
sound  of  a  locust. 

In  addition  to  Invertebrates 
there  were  Fishes  among  Yer- 
tebrates.  The  remains  of  the 
Fishes  are  the  head,  teeth,  large  spines  that  formed  the  front 
margin  of  the  fins,  and  also  the  whole  body  with  its  scales; 
but  never  the  back-bone  (vertebral  column),  as  this  was  car- 
tilaginous and  not  bony,  and  hence  decayed  on  burial. 

The  species  included  are  (1)  Sharks;   (2)  Gars  or  Ganoids; 
and  (3)   intermediate  kinds  called  Placoderms. 

1.  Sharks. — The  remains  of  the  sharks  are  eitner  the  teeth, 
the  shagreen,  or  hard,  rough-pointed    covering   of   the  body, 


Fig.  142. 


Fin-spine  of  a  Shark. 


and  the  large  spines  with  which  the  front  margin  of  the  fins 
are  sometimes  armed.  Fig.  142  represents  one  of  the  fin- 
spines  of  a  shark  of  the  Corniferous  period,  two  thirds  the 
full  length.  The  shark  was  one  of  great  size,  as  the  length 


DEVONIAN  AGE.  145 


of  the  spine  indicates.     Some  of  the  sharks  had  rather  blunt, 
cutting  teeth;  but  the  most  common  kind,  related  to  the  liv-] 
ing  Cestracion   of  Australian   seas,  had   a   pavement   of  bony/ 
pieces   over  the   inner  surface  of  the  lower  jaw,  making  the 
mouth    a    formidable    grinding    apparatus,    fit    for    cracking 
Brachiopods  and  the  like. 

2.  Gars  or  Ganoids. — The  Gar-pikes  of  the  Mississippi  and 
the  Great  Lakes,  now  a  rare  kind  of  Fish  in  the  world,  are 
examples  of  the  type  of  Fishes  that  was  exceedingly  abundant 
in  species  in  the  Devonian  Age.  The  scales  of  Gars  are  bony 
and  shining,  unlike  those  of  ordinary  modern  Fishes,  and  to 
this,  Agassiz's  name,  Ganoid  (from  the  Greek  for  shining), 
refers.  In  many  species  the  scales  are  set  side  by  side  with 
a  special  arrangement  for  interlocking  at  one  margin  after  the 
fashion  of  the  tiles  on  a  roof;  while  in  others  they  are  put 
on  more  like  shingles,  or  in  the  way  common  in  ordinary 
fishes.  Figs.  143,  144  represent  two  Figg  W3.U6> 

kinds  of  tile-like  scales;  and  145,  the  j^g^  ^  us 
under  surface  of  two  of  the  latter, 
showing  how  they  are  secured  to  one 
another.  Figs.  146,  147  represent  two 
specimens  of  the  Ganoid  fishes  of  the 
Devonian.  The  tail  in  Fig.  146  has  a  Scales  of  Ganoids- 

peculiarity  that  belonged  to  all  of  the  ancient  fishes;  that  is, 
the  vertebral  column  extends  to  its  extremity.  In  Meso- 
zoic  and  Cenozoic  species  and  modern  Gars  the  vertebral 


146 


PALEOZOIC  TIME. 


Figs.  146,  147, 


Ganoids. 

Fig.  146,  Dipterus  raacrolepidotus  (X  '/i) ;  147,  Holoptychius ;  147  a,  scale  of  same. 

column    stops    at   the   commencement   of   the   tail-fin,   as  in 
Tig.  148. 

Some  of  the   Ganoids   of  the   Middle  Devonian  whose  re- 
mains have  been  found  in  Indiana  and  Ohio  were  of  great  size. 

Figs.  148,  149. 

149 


Ganoids. 
Fig.  148,  tail  of  Thrissops ;  149,  tooth  of  an  Onychodus. 

One  of  them  had  jaws  a  foot  to  a  foot  and  a  half  long,  with 
teeth  in  the  lower  jaw  (Fig.  149)  two  inches  or  more  long. 


DEVONIAN  AGE. 


147 


A  Devonian  fish  between   a  Ganoid  and   Shark   is   repre- 
sented in  Fig.  150. 


Fig.  150. 


Cephalaspis  Lyellii. 

3.  Placoderms.  —  Still  stranger  forms  are  those  called  Pla- 
coderms.     The  body   of  Fig.    151  is   encased  in   bony   pieces 

Fis?s.  151,  152. 


Placoderms. 
Fig.  151,  Pterichthys  Milleri  (X  #) ;  152,  Coccosteus  decipiens  (X  #)• 

like  that  of  a  Turtle,  and  the   length  of  the   species,  whose^ 
remains  occur  in  Eussia  and   Scotland,   is   supposed  to  havey 


148  PALEOZOIC  TIME. 


been  twenty  to  thirty  feet.     The  term  Placoderm  alludes  to  the 
covering  of  plates,  and  is  from  the  Greek  for  plate  and  skin. 
The  teeth  of  Ganoids  are  usually  very  sharp.      Sometimes 
they  are  small  and  fine,  and  grouped  so  as  to  make  a  brush- 
Fig.  153.  like  surface ;  but  often  they  are  very 
large    and    stout.      The   material   of 
the  interior  of  the  teeth,  called  den- 
tine,  is  intricately  folded,  and  in  allu- 
sion  to  ^  passages  of  a  labyrinth, 
such   teeth   are   said   to   have   within   a   labyrinthine   texture. 
A  simple  form  of  this  labyrinthine  texture  is  represented  in 
Fig.  153. 

The  facts  reviewed  with  reference  to  the  life  of  the  Devo- 
nian teach  that  during  the  progress  of  the  age  the  marshes 
and  dry  land  .were  covered  with  jungles  and  forests;  that  the 
trees  were  without  conspicuous  flowers,  and  the  most  of  them 
with  no  true  flowers  at  all;  that  the  seas  were  brilliant  with 
living  Corals,  as  well  as  Crinoids,  and  abounded  in  Bra- 
chiopods  and  Trilobites ;  that  they  also  had  their  great  fishes,  — 
Sharks,  Gars,  and  Placoderms.  The  land,  too,  had  its  swarms 
of  Insects,  and  probably  also  its  Spiders  to  spread  their  webs 
for  the  May-flies,  although  no  relics  of  them  have  yet  been 
found. 

3.  Mountain-making. 

The  Devonian  age  passed  quietly  for  the  larger  part  of  the 
North  American  continent,  without  any  tilting  of  the  rocks; 


CARBONIFEROUS  AGE.  149 

yet  not  without  wide,  though  small,  changes  of  level,  varying 
the  limits  and  depth  of  the  Interior  sea;  such  changes  of 
level  and  of  limits  being  indicated  by  the  varying  limits  of 
the  rocks,  all  of  which  are  of  marine  origin.  This  quiet  wa*s 
not  interrupted  between  the  Devonian  and  Carboniferous  eras, 
as  far  as  yet  discovered,  except  to  the  northeast  in  the  region 
of  New  Brunswick,  Nova  Scotia,  and  Northeastern  Maine. 
There  an  upturning  and  flexing  of  the  beds  occurred,  and, 
as  a  result,  some  mountain-making. 

The  southward  extension  or  growth  of  the  dry  land  of  the 
continent  continued;  and,  by  the  close  of  the  Devonian,  the 
shore-line  probably  crossed  the  southern  portion  of  what  is 
now  the  State  of  New  York,  —  where  is  the  southern  limit 
of  the  outcropping  Devonian,  so  that  all  of  Canada  except  the 
southwest  extension  north  of  Lake  Erie,  nearly  all  of  New 
York,  and  much  the  larger  part  of  New  England,  were  above 
the  sea-level,  together  with  Wisconsin  and  the  borders  of  the 
adjoining  States.  There  was  probably  also  an  island,  trending 
north-northeast,  over  the  Cincinnati  region  (page  135),  and  an- 
other about  an  Archaean  area  in  Missouri.  See  map,  page  105. 

3.  Carboniferous  Age,  or  Age  of  Coal-Plants. 

The  Carboniferous  age  was  the  time  when  the  most  exten- 
sive coal-beds  of  Europe  and  America  were  formed.  The 
name  Carboniferous  is  from  the  Latin  carbon,  coal. 


150  PALEOZOIC  TIME. 


1.  Rocks.  —  Coal-measures. 

1.  The  age  commenced  with  a  marine  period,  —  the  Subcar- 
boniferous,  —  in  which  a  large  part  of  the  North  American 
continent  was  under  the  sea,  though  not  at  great  depths,  and 
Great  Britain  and  Europe  also  were  to  a  large  extent  sub- 
merged. During  it,  limestone  strata,  with  some  intervening 
sand-beds,  were  in  progress  in  portions  of  Great  Britain  and 
Europe,  and  over  much  of  the  Mississippi  basin  or  the  In- 
terior region;  and,  at  the  same  time,  great  fragmental  depos- 
its, making  sandstones,  shales,  and  conglomerates,  were  laid 
down  along  the  Appalachian  region  from  the  borders  of  New 
York  southwestward,  the  thickness  of  which  was  five  times  as 
V  great  as  that  of  the  limestone  strata. 

The  limestone  was  formed  to  a  great  extent  of  Crinoids,  and 
has  been  called  Crinoidal  limestone.  The  Crinoids  were  of 
numerous  species  and  very  various  forms.  One  of  the  most 
perfect  specimens  is  represented  in  Fig  154,  only  the  stem 
below  being  wanting.  The  figure  shows  the  numberless  stony 
pieces  —  really  blocks  of  limestone  material  —  of  which  it  con- 
sists, and  which  ordinarily  fell  to  pieces  when  the  animal  died, 
as  there  was  little  animal  membrane  to  hold  them  together. 
The  animal  opened  out  its  arms  at  will,  and  when  expanded, 
the  breadth  of  the  flower-like  summit  in  this  species  was 
about  three  inches.  The  stem  below,  when  entire,  was  prob- 
ably a  foot  or  more  long.  The  little  disks  of  which  the  stem 


CARBONIFEROUS  AGE. 


151 


in  Crinoids  consists,  looking  like  button-moulds,  are  common 
fossils  in  the  limestones.  (See  page  34.)  Some  of  them  are 
an  inch  in  diameter.  Fig.  155  represents  another  kind  of 
Crinoid,  which  was  without_ams,  called  a  Pentremites,  from 
the  Greek  for  Jive,  the  form  of  the  stem  being  approximately 
five-sided. 

Figs.  154-156. 


Crinoids.  —  Coral. 
Fig.  154,  Zeacrinus  elegans ;  155,  Pentremites  pyriformis.  —  Coral :  156,  surface  of  Lithostrotion  Canadense. 

There  were  also  Corals;  and  a  top  view  of  the  most  com- 
mon of  these  is  represented  in  Fig.  156.  Brachiopods  also 
contributed  largely  to  the  rock,  as  to  all  earlier  limestones : 
figures  of  two  of  them  are  given  in  Figs.  157,  158. 

2.  After  the  Subcarboniferous  period  —  a  period  of  submer- 
gence —  began  the  true  Coal  period,  or  that  of  the  Coal-meas- 
ures, as  the  series  of  coal-beds  and  rocks  containing  them  is 
called.  The  rocks  are  mostly  sandstones,  shales,  and  conglom-  ) 


152  PALEOZOIC  TIME. 


crates;    but   in  the   Interior   region  of   North  America  there 
/     are  some  intervening  limestone  strata.     The  rock  at  the  base 
of  the   coal-measures   is  generally  a  conglomerate   called   the 
millstone-grit. 


157 


Brachiopods. 

Fig.  157,  Spirifer  bisulcatus  ;  158,  Productus  punctatus. 

The  Coal-beds  contain  only  terrestrial  or  fresh-water  fossils, 
and  nearly  all  are  plants;  while  the  strata  that  separate  them 
have  sometimes  marine  or  brackish  water  fossils. 

The  areas  of  the  coal-measures  are  the  black  areas  on  the 
maps  of  North  America  and  England,  pages  105,  114. 

In  North  America  there  is  one  area,  the  Acadian,  to  the 
northeast  in  Nova  Scotia  and  New  Brunswick;  a  second,  of 
very  small  extent  in  Ehode  Island;  a  third,  the  Alleghany, 
reaching  from  near  the  southern  boundary  of  New  York  over 
part  of  Pennsylvania,  Ohio,  Kentucky,  and  Tennessee  to  Ala- 
bama ;  a  fourth,  in  Central  Michigan ;  a  fifth,  the  Eastern  In- 
terior, covering  parts  of  Illinois,  Indiana,  and  West  Kentucky; 
a  sixth,  the  Western  Interior,  over  parts  of  Iowa,  Missouri, 


CARBONIFEROUS  AGE.  153 

Kansas,  Arkansas,  and  Texas.  The  last  two  were  originally 
united  in  one,  the  Mississippi  valley  now  separating  them. 
It  has  been  estimated  that  the  area  of  the  workable  coal-beds 
of  the  United  States  is  at  least  120,000  square  miles.  The 
coal  area  of  Nova  Scotia  and  New  Brunswick  is  18,000  square 
miles. 

The  principal  coal  areas  of  England  are  those  of  South 
Wales;  the  great  Lancashire  region  east  of  Liverpool  (B,  on 
the  map,  p.  114)  and  Manchester  (C) ;  the  Derbyshire  coal 
region  farther  east;  and  on  the  northeastern  coast,  the  New- 
castle coal-field  (D).  There  are  also  coal-fields  in  Scotland 
between  the  Grampian  range  on  the  north  and  the  Lammer- 
muirs  on  the  south ;  and  others,  of  Ulster,  Connaught,  Leinster 
(Kilkenny),  and  Munster,  in  Ireland.  The  areas  of  England 
and  Scotland  are  supposed  to  have  been  originally  one  great 
coal-field.  There  are  valuable  coal-fields  of  smaller  extent  in 
Belgium,  Prance,  and  Spain,  and  stjll^smaller  in  Germany  andj 
Southern  Russia. 

The  greatest  thickness  of  the  coal-measures  in  Pennsylvania^ 
is  4,000  feet;  in  Illinois,  1,200  feet;  in  Nova  Scotia,  about 
15,000  feet.  In  Great  Britian  it  is  7,000  to  12,000  feet  in 
South  Wales,  and  contains  a  hundred  beds  of  coal ;  7,000 
feet  in  Lancashire,  with  forty  beds  of  coal;  2,000  feet  at 
Newcastle.  The  aggregate  thickness  of  the  coal-beds  of  a 
region  is  not  over  one  fiftieth,  of  that  of  the  coal-measures. 

The  coal-beds  vary  in  thickness  from  less  than  an  inch  to 

7* 


154  PALEOZOIC  TIME. 


30  or  40  feet.  The  " mammoth  vein"  of  the  anthracite  re- 
gion in  Pennsylvania  is  29  feet  thick  at  Wilkesbarre;  but 
there  are  some  layers  of  shale  in  the  course  of  it,  —  a  common 
fact  in  all  coal-beds.  Some  coal-beds  contain  too  much  earthy 
matter  to  be  of  any  value. 

The  mineral  coal  is  of  different  kinds.  That  of  Central 
Pennsylvania  and  of  Rhode  Island  is  anthracite,  while  that 
of  the  rest  of  the  country  is  almost  wholly  bituminous  coal. 
Anthracite  is  a  firm  lustrous  coal/  burning  with  but  little 
flame,  while  the  bituminous  coal,  as  that  from  Pittsburg  and 
the  States  west,  is  less  firm  and  usually  of  less  lustre,  and 
burns  with  much  yellow  flame.  The  flame  is  due  mainly  to 
the  fact  that  part  of  the  carbon  is  combined  with  hydrogen  (or 
with  hydrogen  and  oxygen)  into  a  compound  that,  when  heat 
is  applied,  becomes  a  combustible  gas  or  mineral  oil.  Bitu- 
minous coal  when  heated  affords  more  or  less  of  mineral  oil 
(the  material  from  which  kerosene  is  obtained),  although  it 
\  contains  none ;  the  oil  or  gas  is  produced  by  the  heat  out  of 
some  carbonaceous  material  present.  Some  bituminous  coals 
—  especially  those  compact  coals,  scarcely  shining,  called  can- 
nel  coal — afford  50  per  cent  or  more  of  volatile  matter; 
while  anthracite  yields  very  little,  and  this  is  mostly  the  vapor 
of  water. 

Coals  always  contain  some  impurity  which  is  the  "  ashes " 
and  " clinkers"  of  a  coal-fire.  This  ashes  or  earthy  mate- 
rial was  largely  derived  from  the  plants  themselves,  and  for 


CARBONIFEROUS  AGE.  155 

the  best  coals  wholly  so;  but  in  other  cases  it  is  part  of  the 
detritus  that  was  from  time  to  time  washed  over  the  beds 
of  vegetable  debris  when  they  were  forming.  The  coal-beds 
always  contain  a  little  sulphur,  —  enough  to  give  a  sulphur 
smell  to  the  gases  from  the  burning  coal;  and  the  most  of  it 
comes  from  the  presence  of  _pyrite,  a  compound  of  iron  and 
sulphur. 

The  layer  of  rock  under  a  coal-bed  is  often  a  clayey  layer, 
—  called  the  underclay,  —  and  it  is  frequently  full  of  the 
under- water  stems  or  roots  of  plants.  The  trunks  sometimes 
project  from  the  top  of  a  bed  of  coal,  as  shown  in  Fig.  65, 
page  84.  Many  logs  or  great  trunks  lie  in  the  strata  that 
intervene  between  the  coal-beds,  which  were  once  floating  logs ;  j 
and  multitudes  of  ferns  and  flattened  stems  or  trunks  of  these 
and  other  plants  are  often  spread  out  in  the  shales,  and  espe- 
cially in  the  bed  of  rock  directly  over  a  coal-bed.  Moreover, 
the  coal  itself,  even  the  hardest  anthracite,  has  sometimes  im- 
pressions of  plants  in  it,  and,  more  than  this,  contains  through- 
out its  mass  vegetable  fibres  in  a  coaly  state  which  the 
microscope  can  detect. 

Coal  was  made  from  plants,  and  each  coal-bed  was  origi- 
nally a  bed  of  vegetable  material  like  the  peat-beds  of  the 
present  time  in  mode  of  accumulation.  (See,  on  this  point, 
page  40.)  The  plant-bed  having  accumulated  until  several 
times  thicker  than  the  coal-bed  to  be  made  out  of  it,  was 
finally  covered  with  beds  of  clay  or  sand;  and  while  thus 
buried  it  gradually  changed  to  coal. 


156  PALEOZOIC  TIME. 


Plants  when  dried  are  one  half  carbon,  —  the  chief  material 
of  charcoal,  —  the  rest  being  mostly  the  two  gases  oxygen  and 
hydrogen;  after  the  change,  eight  tenths  to  nine  tenths  or 
more  of  the  whole  are  carbon. 

3.  The  coal-measures  are  followed  in  Europe  by  a  series 
of  red  sandstones  and  clayey  rocks  or  marlytes,  with  a  mag- 
nesian  limestone,  constituting  the  Permian  group,  —  so  called 
from  the  district  of  Perm,  in  Russia.  In  North  America  the 
Permian  rocks  include  the  sandstones  and  shales  at  the  top 
of  the  coal-measures  in  Kansas. 

2.    Life. 

1  Plants.  —  The  plants  were  similar  in  general  character  to 
their  predecessors  in  the  Devonian  age,  though  mostly  dif- 
ferent in  species  and  partly  in  genera.  Of  the  higher  Cryp- 
togams —  called  Acrogens  (or  upward  growers,  as  the  word 
from  the  Greek  signifies) ,  because  they  can  grow  into  trees  — 
there  were  (1)  Ferns,  (2)  Equiseta,  (3)  Lycopods ;  and  of 
the  Phenogams,  or  flowering  trees,  there  were  Conifers,  or  plants 
of  the  Pine-tribe.  The  trees  and  shrubs  grew  luxuriantly 
over  the  almost  endless  marshes  of  the  continent,  and  spread 
also  beyond  them  over  the  higher  lands. 

The  features  of  the  vegetation  and  of  the  ordinary  land- 
scape is  shown  in  the  following  ideal  sketch.  The  tree  at 
the  centre  is  a  Tree-fern,  and  there  are  smaller  Ferns  below. 
The  tree  near  the  left  side  is  a  Lycopod  of  the  ancient  tribe 


CARBONIFEROUS  AGE. 


157 


of  Lepidodendrids ;  and  in  the  right  corner  there  are  other 
Lepidodendrids  and  the  trunk  of  a  Sigillaria.  In  the  left 
corner  there  are  Equiseta.  The  region  is  represented  as  a 


Fij?.  159. 


Carboniferous  Vegetation. 


great  marshy  plain  with  lakes.  The  lakes  of  the  Carbon- 
iferous era  probably  had  their  many  floating  islands  of  vege- 
tation, carrying  large  groves  like  the  floating  islands  of  some 
lakes  in  India. 


158 


PALEOZOIC  TIME. 


Fig.  160. 


Fern. 

Sphenopteris  Gravenhorstii. 


A  portion  of  one  of  the  Perns  is  shown  in  Pig.  160,  and 
of  another  in  Pig.  161.     Pig.  162  represents  one  of  the  Equi- 

Fig.  161. 


Neuropteris  hirsuta. 


seta,  a  species  of  Calamites  (page  140) ;   plants  with  jointed 
stems  that  grew  often  to  a  height  of  20  feet,  and  sometimes 

Fig.  162. 


Equisetum. 
Calamites  cannseforniis. 


CARBONIFEROUS  AGE. 


159 


were  a  foot  in  diameter,  —  very  unlike  the  little  Horse-tails 
of  modern  time. 

The  Lycopods  of  the  tribe  of  Lepidodendrids  had  the  as- 
pect of  Pines  and  Spruces,  and  were  40  to  80  feet  or  more 
in  height.  On  some,  the  slender  pine-like  leaves  were  a  foot 
or  more  long.  Figs.  163,  164  show  the  scars  of  the  outer 


163  - 165. 


163 


Lycopods. 
Fig.  163,  Lepidodendron  clypeatum  ;  164,  Halonia  pulchella ;  165,  Sigillaria  oculata. 

surface  of  two  of  the  Lepidodendrids  arranged,  as  usual,  in 
alternate  order;  and  Eig.  165  those  of  a  Sigillaria  in  vertical 
series.  The  resemblance  of  the  scars  in  the  latter  to  an  im- 
pression of  a  seal  suggested  the  name  Sigillariay  from  the 
Latin  Sigilla,  seal. 

The    cones    of   the    Lepidodendrids    and   Conifers    and   the 
nuts  of  the  latter  also  occur  in  the  beds.     Two  of  these  nuts 


160 


PALEOZOIC  TIME. 


are  represented  in  Figs.  166,  167.  They  are  supposed  to 
have  belonged  to  trees  related  to  the  modern  yew-tree. 

Nearly  500  species  of  Carbonif- 
erous plants  have  been  described 
from  North  America,  and  about 
the  same  number  from  Europe ; 
and  of  these  more  than  one  third 
were  •  common  to  Europe  and 
America. 

There    are    also    coal-regions    in 
the   Arctic  islands   which  have  af- 
Nuts  of  conifers,  forded  some  of  the  same  species  of 

Fig.  166,  Trigonocarpus  tricuspidatus ;   167, 
T.ornatus;  168,  view  of  lower  end  of  same.        plants      that     W6rC      growing      in     Eu- 

rope  and  America,  showing  great  uniformity  in  the  climate 
of  the  era;  a  fact  sustained  also  by  the  occurrence  in  the 
Arctic  deposits  of  many  fossil  shells  and  corals  identical  with 
some  then  living  in  the  seas  of  Europe  and  America. 

2.  Animals.  —  The  seas  of  the  Carboniferous  age  abounded 
in  Crinoids  and  Corals  among  Eadiates,  and  Brachiopods  far 
exceeded  in  number  all  other  kinds  of  Mollusks;  but  in  the 
group  of  Articulates,  while  there  were  many  kinds  of  Worms 
and  Crustaceans,  Trilobites  were  few.  Trilobites  had  been 
replaced  by  other  Crustaceans,  some  of  which  were  much  like 
the  modern  Shrimp.  Examples  of  the  Crinoids,  Corals,  and 
Brachiopods  of  the  earlier  part  of  the  age  are  figured  on 
pages  151,  152. 


CARBONIFEROUS  AGE.  161 

Fishes  were  in  great  numbers  and  of  large  size,  and  they 
belonged  to  the  two  grand  divisions  that  were  especially  char- 
acteristic of  the  Devonian,  —  the  Sharks  (called  also  Sela- 
chians, from  the  Greek  for  cartilage,  the  Sharks  being  fishes 
with  a  cartilaginous  skeleton)  and  the  Ganoids.  One  of  the 
Ganoids  of  the  coal-measures  is  represented  in  Fig.  169.  It 

Figs.  169, 170. 

170, 


Fishes. 

Ganoid  :  Fig.  169,  Eurylepis  tuberculatus,  from  the  coal-formation  in  Ohio.  —  Selachian  :  Fig.  170,  tooth  of 
Carcharopsis  Wortheni ;  a,  profile  of  section  of  same. 

has  the  vertebrated  tail  characteristic  of  all  Paleozoic  fishes. 
Fig.  170  shows  the  form  and  size  of  the  teeth  of  one  of  the 
sharks  of  the  Illinois  region. 

The  land  had  its  Insects,  true  Spiders,  Scorpions,  and  Cen- 
tipedes, and  also  its  land  Snails ;  and  among  the  Insects  there 
were  May-flies,  Cockroaches,  and  Crickets.  A  view  of  one  of 
the  May-flies,  twice  the  natural  size,  is  shown  in  Fig.  171 ; 
of  the  wing  of  a  Cockroach  in  Fig.  172;  of  a  Spider,  from 
Morris,  Illinois,  in  Fig.  173;  and  of  a  Centipede,  from  Nova 
Scotia,  in  Fig.  174. 

Besides  these   species  there  were  also  Reptiles,  the  earliest 


162 


PALEOZOIC  TIME. 


relics  of  which  thus  far  found  come  from  Carboniferous  rocks. 
Footprints  of  them  have  been  described  from  the  Subcarbon- 

Figs.  171-174. 


174 


Terrestrial  Articulates. 

Fig.  171,  Miamia  Bronsoni  (X  2) ;  172,  Blattina  venusta,  wing  of  a  Cockroach.  —Spider  :  Fig.  173, 
Arthrolycosa  antiqua.  —  Centipede  :  Fig.  174,  Xylobius  sigillarise. 

iferous  beds  of  Pennsylvania,  indicating  a  large  animal  having 
a  tail,  —  the  tail  having  made  its  mark  on  the  mud-flat  over 


CARBONIFEROUS  AGE. 


163 


Fig.  175. 


which  the  animal  marched.  In  the  Carboniferous  beds  of 
Illinois,  Ohio,  and  Nova  Scotia  skeletons  have  been  found. 
One  of  them,  from  Ohio,  is  represented  in  Pig.  175.  It 
has  the  broad  cranium  with 
large  open  spaces  that  is 
found  in  the  Erog  and  Sala- 
mander; but  while  modern 
species  have  a  naked  skin 
and  no  teeth,  the  Carbon- 
iferous kinds  were  furnished 
with  scales  and  sharp  teeth 
very  much  like  those  of) 
the  Ganoid  fishes.  Progs' 
and  Salamanders  belong  to 
the  inferior  division  of  Rep- 
tiles called  Amphibians. 
They  are  distinguished  from 
true  Reptiles  (such  as  Liz- 
ards, Crocodiles,  Snakes, 
Turtles)  by  having  gills 
when  young,  which  serve 
them  for  respiration  until 
they  become  full  grown ;  then  the  gills  drop  off,  and  they 
use  their  lungs.  The  Carboniferous  species  are  believed  to 
have  had  this  low  fish-like  character  in  the  young  state,  and 
thus  to  have  been  related  to  the  modern  Frog  and  Salaman- 


164  PALEOZOIC  TIME. 


der,  or  Amphibians;  but,  while  so,  they  were  greatly  superior 
to  the  modern  representatives  of  the  tribe. 

Besides  these  Amphibians,  there  were  also  true  Reptiles. 
Fig.  176  represents  a  vertebra  of  one  of  them,  from  the 

Nova  Scotia  coal-measures.     The 

Figs.  176,  177.  .          . 

vertebra,  as  the  section  in  .big. 
177  shows,  was  concave  on  both 
surfaces  like  those  of  fishes,  and 
also  like  those  of  the  sea-sau- 
rians,  found  in  the  rocks  of  the 
next  geological  age,  —  reptiles 

Fig.  I76,  Vertebra      E™  Acadicus,  Marsh;     that       had       paddleS       like       whaleS. 
177,  profile  of  same.  .,,         -i      />  ,  i         i  •     -\        *> 

Finally,  before  the  last  period  of 

the  Carboniferous  age  had  passed,  there  were  also  still  higher 
Eeptiles,  —  those  that  lived  on  the  land. 

No  remains  of  Birds  or  of  Mammals  have  yet  been  found 
in  any  rocks  as  early  as  those  of  the  Carboniferous  age. 

3.    Changes  during  the  Progress  of  the  Carboniferous  Age. 

Changes  of  level  were  going  on  over  the  North  American 
continent  throughout  the  Carboniferous  age;  but  they  were 
oscillations  above  and  below  the  sea-level  in  many  alternations, 
and  of  the  gentlest  and  slowest  kind  possible,  and  not  uplift- 
ings  into  mountains.  Just  such  alternations  of  level  had  been 
in  progress  all  through  the  preceding  ages;  but  the  Carbon- 
iferous movements  were  peculiar  in  this,  that  the  continent 


CARBONIFEROUS  AGE.  165 

over  its  broad  surface  was  just  balancing  itself  near  the  wa- 
ter's  surface,  —  part  of  the  time  bathing  in  it  and  then  out 
in  the  free  air,  and  so  on,  alternately;  while,  in  former  times, 
the  oscillations   seldom  carried  the  interior  region  out  of  the 
sea,  or  if  it  did,  only  portions  at   a  time.     It  was   peculiar 
also  in  the  fact  that  the  wide  continent  lay   quiet  above  the 
sea-level,  with  a  nearly  even  surface,  for  a  very  great  period 
of  time,  —  sufficiently  long  to  make  beds  of  vegetable  debris 
thick  enough  for  coal-beds;   many   of  the   coal-beds   are  six 
feet  thick,  and  some  twenty  or  more ;  and  even  six  feet  would  ( 
require,  according  to  an  estimate  that  has  been  made,  a  bedh 
thirty  feet  thick  for  bituminous  coal,  and  a  much  thicker  one/ 
for  anthracite. 

The  Interior  of  the  continent  from  Eastern  Pennsylvania  to 
Central  Kansas  was  a  region  of  vast  jungles,  lakes  with  float- 
ing grove-islands,  and  some  dry-land  forests,  and  the  debris 
of  the  luxuriant  vegetation  produced  the  accumulating  plant- 
beds.  A  Cincinnati  area  of  emerged  land  then  divided  the 
continental  marsh  from  Lake  Erie  to  Tennessee;  but  farther^ 
south  the  eastern  and  western  portions  were  probably  united.  J 
The  Michigan  coal  area  was  an  independent  marsh  region. 
The  Green  Mountains  separated  the  Pennsylvania  area  from 
those  of  New  England  and  Nova  Scotia;  but  the  two  latter 
were  probably  connected  along  the  region  of  the  Bay  of  Fundy 
and  Massachusetts  Bay. 

The  changes  of  level  could  hardly  have  carried  up  evenly 


166  PALEOZOIC  TIME. 


all  parts  of  the  Interior  marsh-region  from  Pennsylvania  to 
beyond  the  Mississippi;  and  it  is  evident  that  they  did  not, 
since  it  is  difficult  to  make  out  the  parallelism  between  the 
beds  of  the  eastern,  central,  and  western  portions. 

The  era  of  verdure  during  which  a  plant-bed  was  in  pro- 
gress finally  came  to  its  end  by  a  return  of  the  salt  water 
over  the  continental  interior  which  destroyed  the  terrestrial 
life;  and  then  began  the  deposition  of  sediment  covering  up 
the  plant-beds  and  making  sandstones  or  shales  or  conglom- 
erates, or  the  forming  of  limestones.  Finally,  the  continental 
surface,  or  wide  portions  of  it,  again  emerged  slowly,  putting 
an  end  to  its  marine  life,  and  opening  a  new  era  of  verdure. 
Such  alternations  continued  until  all  the  successive  coal-beds 
were  made ;  some  of  them  affecting  perhaps  the  whole  breadth 
of  the  Interior  coal  area,  others  more  local.  Thus  the  era  was 
one  of  constant  change ;  yet  change  so  gradual  that  only  a  being 
whose  years  were  thousands  or  tens  of  thousands  of  our  years 
would  have  been  able  to  discover  that  any  was  in  progress. 

In  Nova  Scotia  the  oscillations  went  on  until  nearly  15,000 
feet  of  deposits  were  formed;  and  in  that  space  there  are  76 
coal-seams  and  dirt-beds;  and  therefore  76  levels  of  verdant 
fields  between  the  others  when  the  waters  covered  the  land. 
But  over  that  region  the  waters  submerging  the  region  were 
mainly  fresh  or  brackish  waters,  since  no  marine  shells  exist  in 
the  beds,  while  there  are  land  shells  and  bones  of  reptiles. 
The  area  was  an  immense  delta  in  the  Carboniferous  age  at 


APPALACHIAN  REVOLUTION.  167 

the  mouth  of  the  St.  Lawrence,  then  the  only  great  river  of 
the  continent,  and  the  submergences  were  connected  with  the 
floods  of  the  stream  as  well  as  changes  of  level  in  the  crust 
of  the  earth  beneath. 

The  Permian  period,  or  the  closing  part  of  the  Carbonifer- 
ous age,  was  an  era  of  gradual  submergences,  without  long 
eras  of  verdure  or  the  formation  of  plant-beds. 

4.    Mountain-making  at  the  close  of  Paleozoic  Time. 

From  the  beginning  of  Paleozoic  time  to  its  close  all  changes 
over  the  Appalachian  region  west  of  the  Archaean  ridges,  south- 
west of  New  England,  and  over  the  great  Interior  region  of  the 
continent,  had  gone  on  quietly,  with  gentle  oscillations  of  the 
surface  and  slight  displacements,  but  no  general  upturning  in 
any  part. 

These  ages  of  quiet  and  regular  work  in  rock-making  were  1 
very  long,  for  Paleozoic  time   includes   at  least  three  fourths  J  V 
of  all  time  after  the  commencement  of  the  Paleozoic. 

Over  the  Appalachian  region  from  New  York  southward, 
the  Silurian,  Devonian,  and  Carboniferous  deposits  have  great 
thickness.  The  amount  in  Pennsylvania  and  Virginia  has  been  ' 
estimated  at  40,000  feet,  or  over  seven  miles.  But  over  the 
Interior  region,  where  limestones  were  the  most  of  the  time 
forming,  the  thickness  is  from  3,000  to  4,000  feet.  These 
Appalachian  deposits,  more  than  ten  times  thicker  than  those 
of  the  Interior,  were  accumulating  there  for  the  making  of  a 


168  PALEOZOIC  TIME. 


range  of  mountains;  and  at  the  close  of  the  Paleozoic  all  was 
ready  and  the  mountains  were  made. 

These  40,000  feet  of  deposits  were  laid  down  in  a  great 
trough  made  by  the  gradual  sinking  of  the  earth's  crust.  Eor 
the  lowest  sandstone  of  the  series  bears  evidence  that  it  was 
made  in  shallow  waters,  as  stated  on  page  116;  and  the  last 
in  the  series,  the  Carboniferous  beds,  were  spread  out  hori- 
zontally just  above  or  just  below  the  surface,  the  coal-beds 
proving  a  small  emergence  part  of  the  time,  and  ripple-marks, 
mud-cracks,  and  footprints  indicating  that  the  sea-level  was 
near  by.  The  coal-measures  contain  beds  of  iron  ore  of  great 
economical  importance;  and  these  are  evidence  that  the  con- 
dition was  at  times  that  of  a  great  muddy  marsh,  probably  a 
salt  marsh,  the  iron  ore  being  a  marsh  deposit. 

If,  then,  the  top  and  bottom  strata  were  made  near  the 
water-level,  there  must  have  been  seven  miles  of  sinking  dur- 
ing the  interval  between  their  deposition.  Other  beds  of  the 
series  bear  like  evidence  of  shallow- water  origin;  so  that  the 
fact  is  clear  that  the  earth's  crust,  along  what  is  now  the 
region  of  the  Alleghany  Mountains,  west  of  the  Blue  Ridge, 
for  a  breadth  of  nearly  a  hundred  miles  and  a  length  of  seven 
hundred  and  fifty  or  more,  was  slowly  sinking,  —  so  slowly 
that  the  sediments  laid  down  kept  the  trough  all  the  time 
full  to  the  surface,  or  nearly  so. 

This  sinking  of  the  earth's  crust  over  the  region,  and  the 
concurrent  accumulation  of  sedimentary  beds,  were  the  pre- 


APPALACHIAN  REVOLUTION.  169 

paratory  steps  in  the  mountain-making  that  was  then  to  go 
forward,  —  and  steps  that  took,  as  above  remarked,  three  fourths 
of  all  geological  time  after  the  Archaean  era. 

The  catastrophe  consisted  in  the  (1)  folding,  (2)  fracturing, 
(3)  solidifying,  and  in  part  (4)  crystallizing  of  the  beds;  and 
also  (5)  in  the  change,  in  Central  Pennsylvania,  of  bitumi- 
nous coal  to  anthracite. 

The  folds  were  numerous,  and  involved  the  whole  breadth 
of  the  region;  and  if  their  tops  had  not  since  been  worn  off 
by  the   action   of  water,  some   of  the  folds  would   now  rise  \ 
over    10,000    feet    above   the   sea-level.     Their  characters   are  j 
shown   in   Fig.    178,  of   a   section   from   Virginia,   extending 

Fig.  178. 

•fly  •#  -  •  ^yy^^^^^.x.--.^^^ 

from  the  southeast  on  the  right  to  the  northwest  on  the  left, 
over  a  distance  of  six  miles.  It  presents  an  example,  as 
explained  on  page  84,  of  the  denudation  the  country  has 
undergone,  as  well  as  of  the  folding. 

The  coal-formation  was  involved  in  the  folds,  —  a  fact 
which  proves  that  the  folding  began  after  the  coal-beds  were 
formed.  Pig.  179  is  a  section  from  the  vicinity  of  Potts- 
ville,  Pennsylvania,  P  being  the  position  of  Pottsville  on  the 
coal-measures.  Pig.  180  represents  another  from  near  Nes- 
quehoning,  Pennsylvania,  showing  the  anthracite  beds  doubled 
up,  and  in  part  vertical. 

8 


170 


PALEOZOIC  TIME. 


1.  The  folds  are  steepest  and  most  numerous  to  the  south- 
eastward, or  toward  the  ocean,  and  diminish  to  the  northwest- 
ward. (See  Fig.  178.) 

Figs.  179,  180. 


Sections  of  the  Coal-measures. 

Fig.  179,  on  the  Schuylkill,  Pa.  ;  P,  Pottsville  on  the  coal-measures  ;  14,  the  coal-measures  ;  13  to  n,  Devonian 
formations ;  8  to  5,  Upper  Silurian ;  4  to  2,  Lower  Silurian.  Fig.  180,  Anthracite  region,  near  Nesquehon- 
ing,  Pa. ;  the  black  lines  coal-beds. 

2.  The  folds  generally  have  the  western  slope  steepest,  as 
if  pressure  from  the  direction  of  the  ocean  had  pushed  them 
westward;  and  sometimes  the  tops  have  thus  been  made  to 
overhang  the  western  "base.  (Fig.  179.) 

Fig.  181.  I 


Section  of  the  Paleozoic  Formations  of  the  Appalachians,  in  Southern  Virginia,  between  Walker's 
Mountain  and  the  Peak  Hills  (near  Peak  Creek  Valley). 

F,  fault ;  a,  Lower  Silurian  limestone  ;  b,  Upper  Silurian  ;  c,  Devonian ;  d,  Subcarboniferous,  with  coal-beds. 

3.  The  rocks  were  also  fractured  on  a  grand  scale,  and 
those  of  the  eastern  side  of  the  fracture  shoved  up  so  as  to 
make  faults  in  some  cases  of  more  than  10,000  feet.  Fig. 


APPALACHIAN  REVOLUTION.  171 

181  represents  one  of  these  great  faults.  The  fault  is  at  F; 
to  the  right  of  F  is  the  coal-formation,  and  to  the  left,  a  bent- 
up  Lower  Silurian  limestone;  so  that  a  Lower  Silurian  rock 
is  brought  up  to  a  level  with  the  coal-formation,  —  a  lift,  ac- 
cording to  Lesley,  of  20,000  feet. 

4.  The  rocks   were   solidified  through  the  aid  of  the  heat 
caused  by  the  movement   of  the  rocks    (page   72) ;    and  by 
the   same  means  the   change   of    the   coal  to   anthracite  was 
caused.     This  change  to  anthracite  took  place  where  the  rocks 
are  most  upturned;   it  diminished  westward,  and  accordingly 
the  coal,  on  going  west,  is  first  a  semi-anthracite  or  a  semi- 
bituminous  coal,  and  then  true  bituminous  coal,  as  at  Pitts- 
burg.     The  rocks  in  some  regions  were  crystallized. 

5.  While  there  was  so  much  folding  and  fracturing,  there 
was  no  chaotic  confusion  of  the  rocks   produced,  the  stratifi- 
cation being  perfectly  retained. 

It  follows  from  the  facts  (1)  that  the  force  acted  quietly, 
or  with  extreme  slowness,  —  for  otherwise  confusion  would 
have  been  produced;  and  (2)  that  the  pressure  acted  from 
the  direction  of  the  ocean,  —  the  forms  of  the  folds  and  their 
greater  numbers  and  steepness  in  that  direction  proving  this. 

Now,  what  was  the  action  producing  the  folding  and  accom- 
panying effects? 

The  earth's  crust  below  the  region  rested  at  the  time  on 
liquid  rock;  if  it  did  not,  the  trough  7  miles  in  depth 
could  not  have  been  made  by  the  downward  bending  of  the 


172  PALEOZOIC  TIME. 


crust.  Suppose  the  thickness  of  the  crust  to  have  been  at  the 
time  100  miles;  and  that  below  100  miles  there  was  fusion 
and  the  temperature  of  fusion.  In  the  making  of  the  trough 
the  crust  was  bent  downward,  and  as  it  formed  it  was  kept 
full  of  sedimentary  beds;  so  that,  at  the  close  of  the  Car- 
boniferous age,  the  distance  from  the  surface  to  the  original 
bottom  of  the  bent  crust  was  increased  by  7  miles,  making 
it  107  miles.  If,  then,  the  distance  down  to  the  temperature 
of  fusion  was  100  miles,  the  bottom  of  the.  crust  beneath  the 
trough  for  a  thickness  of  7  miles  must  have  been  wholly 
or  partly  melted  off.  The  crust  would  have  been  greatly 
weakened  by  such  a  loss,  and  also  by  the  heat  penetrating 
upward  into  it;  for  it  had  received  no  corresponding  increase 
of  strength  from  the  7  miles  of  deposits  added,  since  these 
were  not  wholly  consolidated.  As  a  consequence,  the  pressure 
from  the  direction  of  the  ocean,  resulting  from  the  earth's 
contraction  (page  89),  the  same  that  had  been  making  the 
trough,  produced  finally  a  break  below  and  a  collapse,  and 
thereby  a  pressing  together  of  the  thick  deposits  lying  in  the 
trough,  folding  and  breaking  them ;  and  also  raising  the  upper 
surface  above  its  previous  level,  because  the  width  of  the  base 
on  which  they  rested  was  narrowed  by  the  collapse. 

These  facts  respecting  the  formation  of  the  Alleghany  Moun- 
tains illustrate  the  way  in  which  other  mountains  of  folded 
rocks  have  been  made.  The  Green  Mountains  had  a  similar 
history :  first,  a  slow  subsiding  of  the  crust  making  a  trough, 


APPALACHIAN  REVOLUTION.  173 

and  a  trough  that  was  kept  full  of  sedimentary  deposits,  and 
which  took  the  whole  of  the  long  Lower  Silurian  era  for  its 
completion  (probahly  half  the  whole  length  of  Paleozoic 
time) ;  then  a  break  below,  and  a  collapse  producing  folds 
and  fractures  throughout  the  region;  contemporaneously,  the 
production  of  heat  as  a  consequence  of  the  friction  of  the 
folding  and  fracturing  rocks,  which  was  added  to  the  heat 
that  had  come  up  into  the  strata  from  the  depths  below  dur- 
ing the  sinking;  and  the  solidification  and  metamorphism  of 
the  various  rocks  as  a  consequence  of  the  heat. 

Mountains  were  made  in  Europe  and  Great  Britain  at  the 
same  time  with  the  Alleghanies,  so  that  the  close  of  Paleozoic  f 
time  has  its  mountain  boundary  elsewhere  besides  in  America.  S 

Changes  in  Paleozoic  Life  at  the  Close  of  the  Era. 

In  Paleozoic  time  Crinoids,  Brachiopods,  Cyathophylloid 
Corals,  Orthocerata,  Trilobites,  vertebrate-tailed  Ganoid  Pishes, 
and  Lepidodendrids,  Sigillarids,  and  Calamites  among  plants, 
were  characteristic  species  in  each  of  the  classes  to  which 
they  belong.  With  the  close  of  it,  Trilobites,  Lepidodendrids, 
and  Sigillarids  became  extinct;  Cyathophylloid  Corals,  Ortho- 
cerata, and  vertebrate-tailed  Ganoids  nearly  so;  and,  after- 
ward, Brachiopods  among  Mollusks,  and  Crinoids  among 
Radiates,  were  greatly  inferior  in  numbers  and  importance  to 
other  types  of  more  modern  character.  It  is  thus  that  the 
Paleozoic  features  of  the  world  passed  by. 


174  MESOZOIC  TIME. 


The  characteristics  of  the  following  era,  the  Mesozoic,  had 
in  part  appeared  before  the  Paleozoic  era  closed.  Eor  Am- 
phibians and  true  Eeptiles  were  then  in  existence,  —  Shrimps 
and  other  species  among  Crustaceans  and  Insects,  Spiders,  and 
Centipedes  among  Articulates.  And  the  grand  division  of 
plants  which  had  its  maximum  display  in  the  Mesozoic  — 
the  Cycads,  of  which  an  account  is  given  beyond  —  had  some 
species  before  the  age  closed. 

The  extinction  of  species  at  the  close  of  the  Paleozoic  was 
so  nearly  universal  that,  thus  far,  no  fossils  of  the  Carbonif- 
erous age  have  been  found  in  rocks  of  later  date.  But  the 
rocks  now  in  view  were  those  that  were  made  over  the  conti- 
nental seas,  and,  more  correctly,  over  only  portions  of  those 
seas;  and  hence  they  give  no  facts  as  to  the  species  of  the 
ocean,  and  but  an  imperfect  record  of  those  of  the  continental 


III.  — Mesozoic  Time. 

MESOZOIC  TIME  includes  only  one  age,  —  the  age  of  Eeptiles. 
The  Mesozoic  areas  on  the  maps  of  the  United  States  and  Eng- 
land, pages  105  and  178,  are  lined  obliquely  from  the  right 
above  to  the  left  below. 

Age  of  Reptiles. 

This  age  is  divided  into  three  periods :  — 

1.  The  TRIASSIC:  named  from  the  Latin  tria,  three,  in 
allusion  to  the  fact  that  the  rocks  in  Germany  have  three 
subdivisions. 


REPTILIAN  AGE.  175 


2.  The  JURASSIC  :  named  after  the  Jura  Mountains,  on  the 
eastern  borders  of  Erance. 

3.  The  CRETACEOUS  :  named  from  the  Latin  creta,  chalk,  the 
formation  including  the  chalk-beds  of  England  and  Europe. 

1.  Rocks. 

By  the  close  of  the  Paleozoic,  the  Interior  region  of  the 
American  continent  east  of  the  Mississippi  had  become  dry 
land.  Accordingly,  Triassic  and  Jurassic  rocks  were  formed 
only  on  the  Atlantic  border  east  of  the  Appalachians,  and 
over  the  western  half  of  the  continent  beyond  Missouri. 

These  rocks  on  the  Atlantic  border  cover  long  narrow  areas 
parallel  with  the  Appalachians  from  the  Gulf  of  St.  Lawrence 
southwestward.  One  of  them  lies  along  the  east  side  of  the 
Bay  of  Fundy ;  another  in  the  Connecticut  valley  from  Northern 
Massachusetts  to  New  Haven  on  Long  Island  Sound ;  another, 
commencing  in  the  region  of  the  Palisades,  extends  through 
New  Jersey  and  Pennsylvania  into  Virginia;  and  others  occur 
in  Virginia  and  North  Carolina.  These  areas  are  indicated  on 
the  map  on  page  105. 

The  rocks  are  mainly  red  sandstones.  In  Virginia,  near  Eich- 
mond,  and  in  the  Deep  River  region,  North  Carolina,  there  are 
thick  beds  of  good  mineral  coal.  They  contain  no  marine  fos- 
sils ;  the  few  that  occur  are  either  brackish-water  or  fresh- water. 
It  follows,  hence,  that  the  long  narrow  ranges  of  sandstone  were 
formed  in  valleys,  parallel  with  the  Appalachians,  into  which, 
for  some  reason,  the  sea  did  not  gain  full  entrance. 


176  MESOZOIC  TIME. 


In  Western  Kansas,  and  farther  west  over  the  Bocky  Moun- 
tain region,  there  are  red  sandstone  strata  of  great  extent, 
often  containing  gypsum,  but  generally  without  fossils,  that  are 
regarded  as  Triassic.  Fossils  have  been  found  in  rocks  of  this 
period  in  California,  and  also  in  British  Columbia  and  Alaska. 

Jurassic  beds,  with  marine  fossils,  overlie  the  Triassic  of  the 
Eocky  Mountain  region,  west  of  the  summit,  making  in  part 
the  Wahsatch  Mountains,  the  Sierra  Nevada,  and  other  ranges. 

At  the  close  of  the  Jurassic  period  a  great  geographical 
change  took  place  in  Eastern  North  America  and  also  west  of 
the  Mississippi;  for  in  the  Cretaceous  period  beds  full  of 
marine  fossils  were  forming  all  along  the  Atlantic  border 
south  of  New  York,  and  over  a  wide  region  bordering  the 
Gulf  of  Mexico;  up  the  Mississippi  valley,  to  the  mouth  of 
the  Ohio;  from  Texas  northward  over  Kansas  and  a  large 
part  of  the  eastern  slope  and  summit  region  of  the  Eocky 
Mountains,  perhaps  reaching  to  the  Arctic;  and  also  along 
the  Pacific  border  west  of  the  Sierra  Nevada.  The  outline 
of  the  continent  when  these  beds  were  in  progress  is  shown 
in  the  accompanying  map  (Fig.  182),  the  shaded  portion  be- 
ing the  part  that  was  then  under  water,  filled  with  Cretaceous 
life  and  receiving  Cretaceous  deposits  of  sediment. 

The  Cretaceous  beds  are  mostly  soft  green  and  gray  sand- 
stones, partly  compact  shell-beds  and  "  rotten "  limestone, 
with  hard  limestone  in  Texas,  and  chalk  in  Western  Kansas. 
Marine  fossils  are  abundant,  and  they  generally  indicate  shallow 


REPTILIAN  AGE. 


177 


waters.     Over  the  Bocky  Mountain  region  the  beds  are  in  some 
places  10,000  feet  above  the  sea;  showing  that  the  mountains/ 

« —  -p—  ^  |H* 

have  been  elevated  to  this  extent  since  the  beds  were  made.    ' 

Fig.  182. 


North  America  in  the  Cretaceous  Period. 
MO,  Upper  Missouri  region. 

In  Great  Britain  the  Triassic  beds  (No.  6  on  the  accom- 
panying map,  Fig.  183)  were  red  argillaceous  sandstones  and 
clay  rocks  (marlytes)  formed  in  a  partly  confined  sea-basin.  At 
Cheshire  they  contain  a  bed  of  rock-salt  derived  from  the  evapo- 
ration of  the  waters  of  the  sea-basin.  The  Jurassic  rocks  con- 
sist^ below,  of  a  limestone  called  the  Lias  (No.  7  a) ;  other 
8*  L 


178 


MESOZOIC  TIME. 


Fig.  183. 


Geological  Map  of  England. 

The  areas  lined  horizontally  and  numbered  i  are  Silurian.  Those  lined  vertically  (2),  Devonian.  Those 
cross-lined  (3),  Subcarboniferous.  Carboniferous  (4),  black.  Permian  (5).  Those  lined  obliquely  from 
right  to  left,  Triassic  (6),  Lias  (7  a),  Oolyte  (7  6),  Wealden  (8),  Cretaceous  (9).  Those  lined  obliquely  from 
left  to  right  (10,  n),  Tertiary.  A  is  London ;  B,  Liverpool ;  C,  Manchester ;  D,  Newcastle. 

limestones    above    called    Oolyte    (7   b),  part   of   which   is    a 


REPTILIAN  AGE. 


179 


coral-reef  limestone,  showing  that  there  were  coral-reefs  in  the 
British  seas  of  the  era ;  and  near  and  at  the  top  of  the  series, 
fresh-water  or  soil  beds,  called  the  Portland  dirt-bed,  and  the 
Wealden  (No.  8).  The  oolyte  is  so  named  from  the  occur- 
rence of  beds  of  limestone  which  are  made  of  minute  spheri- 
cal concretionary  grains,  of  the  size  of  the  roe  of  a  small  . 
fish,  the  word  coming  from  the  Greek  for  egg. 

As  the  Jurassic  ended  there  were  large  areas  of  dry  land  and 
marshes  in  Southeastern  England.  But  with  the  commence- 
ment of  the  Cretaceous  period  there  was  a  new  submergence, 
and  green  and  gray  sand-beds  were  accumulated,  followed  by 
a  deeper  submergence  and  the  formation  of  about  1,200  feet  I 

Figs.  184-187. 


Rhizopods. 

Fig.  184,  Lituola  nautiloidea ;  185,  Flabellina  rugosa  ;  186,  Chrysalidina  gradata ;  188,  Cuneolina  pavonia. 

of  chalk,  the  upperjart  containing  flint  nodules.  The  chalk  \ 
consists  very  largely  of  the  shells  of  Ehizopods,  species  not 
larger  than  fine  grains  of  sand,  some  of  which  are  here  fig- 
ured, much  enlarged;  and  since,  as  stated  on  page  34,  similar 
beds  of  Rhizopods  are  now  in  progress  over  the  bottom  of 
the  Atlantic  west  of  Ireland,  and  the  Sponges  and  some  other 
fossils  of  the  chalk  are  probably  deep-water  species,  it  is  be- 


180 


MESOZOIC  TIME. 


lieved  that  the  chalk  was  formed  at  depths  not  less  than 
1,000  feet.  The  flint  of  the  chalk  was  made  from  the  sili- 
ceous Sponges,  spicules  of  Sponges,  and  Diatoms  of  the  same 
sea-bottom. 

2.  Life. 

L  Plants,  —  The  forests  of  Mesozoic  time  contained  Conifers 
and  Tree-Ferns,  like    the  Carboniferous,  but    were    especially 

Fig.  188. 


Cycas  circinalis  (X 


characterized  by  Cycads,  —  plants  that  looked  like  Palms,  as 
the  figure   on  page  180   shows,  but  were  Gymnosperms,  like 


-REPTILIAN  AGE. 


181 


the    Conifers.     Hence    the    forests    of   the    early   and   middle 
Mesozoic  consisted  chiefly  of  Tree-ferns,  Conifers,  and  Cycads ;  \ 
and  where  the  Tree-ferns  and  Cycads  predominated  the  aspect  j) 
was  much  like  that  of  modern  groves  of  Palms. 


189-192. 


Angiosperms  (or  Dicotyledons). 
Fig.  189,  Leguminosites  Marcouanus  ;  190,  Sassafras  Cretaceum ;  191,  Liriodendron  Meekii ;  192,  Salix  Meekii. 

In  the  Cretaceous  beds  occur  the  first  evidence  of  the  ex- 
istence, in  the  world,  of  actual  Palms  and  of  plants  and  trees 
now  so  common,  related  to  the  Elm,  Maple,  and  other  trees 
with  net-veined  leaves,  —  species  which  have  the  seeds  in  a 
seed-vessel,  and  which  are  therefore  called  Angiosperms,  from 


182 


MESOZOIC  TIME. 


the  Greek  for  vessel  and  seed.  A  few  leaves  from  the  Creta- 
ceous of  the  United  States  are  represented  in  Pigs.  189  to  192. 
The  forests  still  had  in  some  places  their  numerous  Cycads; 
but  their  general  character  was  changed,  and  for  the  first  time 
they  looked  modern. 

2.  Animals.  —  The  Corals  and  other  Radiates  had  for  the 
most  part  a  general  resemblance  to  those  of  the  present  era, 
although  all  were  extinct  and  mostly  of  extinct  genera.  The 
same  is  true  of  the  Mollusks,  and  yet  some  kinds  under  these 
classes  were  especially  Mesozoic  in  type. 

This  is  eminently  true  of  the  higher  division  of  Mollusks, 
the  Cephalopods.  The  chambered  shells  of  this  tribe,  repre- 
sented by  Orthocerata,  Nautili,  and 
some  related  species  in  the  Silurian, 
were  in  vast  numbers  under  the 
type  of  Ammonites,  while  there  were 
also  many  Nautili.  Fig.  193  repre- 
sents a  front  view  and  194  a  side 

_.,       _        .    ,          ,   view  of  one  of  the  earlier  of  these 
V  J    Ammonites,  —  a     Triassic     species. 

The  animal  occupied  the  outer  cham- 
ber of  the  shell,  as  in  the  Nauti- 
lus (Fig.  110,  page  123).  Fig.  193 
shows  the  partition  which  was  the  bottom  of  this  outer  cham- 
ber. Around  its  sides  there  are  pocket-like  depressions  into 
which  the  mantle  of  the  animal  descended  to  enable  it  to  hold 


Figs.  193,  194. 


Cephalopod. 

Fig.  193,  Ammonites  tornatus  ;  194,  side  view 
of  same  reduced  to  one  half. 


REPTILIAN  AGE. 


183 


on  to  its  shell.  Two  other  species  of  Ammonites  are  repre- 
sented in  Eigs.  195  - 197.  Fig.  196  shows  the  pockets  in  the 
outer  chamber  of  195.  Pig.  197  represents  a  species  with  the 
outer  edge  unbroken  and  much  prolonged.  The  pockets  are 
depressions  in  the  partitions  at  their  margins.  There  were 
some  Devonian  and  Carboniferous  species,  called  Goniatitet,  that 

Figs.  195  - 197. 


1 96 


Cephalopoda. 

Fig.  195,  Ammonites  Bucklandi,  from  the  Lias  ;  196,  same  in  profile,  showing  outer  chamber  and  its  pockets ; 
197,  A.  Jason,  from  the  OSlyte. 

had  such  pockets,  but  the  pockets  were  simple  in  outline; 
those  of  the  Ammonites  are  very  irregularly  plicated  within. 
Their  complicated  outline  is  well  shown  in  Fig.  198,  repre- 
senting the  series  along  half  the  margin  of  a  partition  in  a 
Cretaceous  species,  the  shaded  part  a  to  6  being  half  of  the 
series  of  pockets,  twice  the  natural  size,  and  b  6  the  middle 


184  MESOZOIC  TIME. 


r  line    of  the   back  of  the   shell.     Among    the    Ammonites   of 
**  \  the  Cretaceous  there  were  species  four  feet  in  diameter. 


Fig.  198. 


Series  of  pockets  in  Ammonites  placenta. 


Besides  these  there  were  other  kinds  of  Cephalopods  having 
internal  shells  or  bones  and  called  Belemnites.  One  of  these, 
from  the  Cretaceous  of  New  Jersey,  is  represented  in  Fig.  199, 
but,  as  usual  with  the  fossils,  it  is  imperfect,  the  upper  slen- 
der part  being  broken  off.  Pig.  200  shows  a  side  view  of 
the  bone  complete,  as  it  has  been  found  in  some  species. 
The  bone  has  the  same  relation  to  the  animal  as  the  pen 
(Fig.  202)  in  the  modern  Squid  (Fig.  201),  it  being  internal 
and  lying  in  the  mantle  along  the  back;  the  animal  of  the 
Belemnite  was  much  like  a  Squid. 

These  Cephalopods  were  in  great  numbers  in  the  seas,  over 
a  thousand  species  having  been  found  fossil.  In  view  of 
their  abundance  it  is  a  remarkable  fact  that  no  Belemnite 
and  only  one  Ammonite  is  known  to  have  lived  after  the 
close  of  the  Cretaceous,  and  we  have  no  evidence  that  by  the 
close  of  the  first  period  of  the  Tertiary  even  one  was  living. 
These  highest  of  Mollusks '  thus  passed  their  climax  during 
the  Mesozoic  era. 


REPTILIAN  AGE. 


185 


The  Vertebrates  included  not  only  Fishes  and  Beptiles,  like 
the  Carboniferous  age,  but  also  Birds  and  Mammals. 

Figs.  199-202. 


Cephalopoda. 

Fig.  199,  Belemnitella  mucronata,  broken  at  top ;  200,  a  Belemnite  with  the  upper  part,  a  b,  perfect ;  201, 
modern  Calamary  or  squid,  Loligo  vulgaris  ;  202,  pen  or  internal  bone  of  same. 

Fishes.  —  Ganoids  and  Sharks  were  the  prevailing  kinds  of 
the  Mesozoic  until  the  Cretaceous  era,  and  then  fishes  of 
modern  type  —  Herring,  Salmon,  Perch,  and  the  like  —  were  in 


186  MESOZOIC  TIME. 


great  numbers,  —  species  that  have  lony  and  not  cartilaginous 
skeletons,  and  which  are  therefore  called  Teliosts,  meaning 
bony  throughout.  They  include  the  common  edible  species. 

The  Ganoids  lost  their  tails,  that  is,  the  vertebrated  char- 
acter of  the  tail-fin,  in  the  first  period  of  the  Mesozoic.  Some 
species  had  then  a  vertebrated  tail,  some  half-vertebrated,  and 
others  non- vertebrated,  that  is,  had  merely  a  caudal  fin;  but 
after  the  Triassic,  all  were  of  the  modern  non-vertebrated  type. 

Reptiles.  —  Eeptiles  were  the  dominant  species  of  the  era 
through  all  the  periods. 

In  the  Triassic,  the  Amphibians  were  of  great  size,  as  shown 
by  their  footprints  on  the  sandstones  of  the  Connecticut  val- 
ley and  at  some  other  localities,  and  also  by  the  bones  that 
have  occasionally  been  found.  Some  of  the  largest  of  them 
walked  as  bipeds  on  feet  that  made  tracks  16  to  20  inches 
long  and  nearly  as  broad,  and  with  a  stride  of  three  feet, 
indicating  a  height  of  at  least  10  or  12  feet.  Pig.  203 
shows  the  form  of  the  impressions.  The  tracks  of  the  much 
smaller  forefeet  are  occasionally  found,  showing  that  this  huge 
biped  Amphibian  sometimes  brought  them  to  the  ground;  the 
form  is  shown  in  Pig.  203  a.  Twenty -two  consecutive  tracks 
of  one  of  these  bipeds  were  laid  open  in  1874  at  one  of  the 
quarries  of  Portland,  Connecticut.  Other  species  have  smaller 
tracks,  and  some  are  less  than  half^an  inch  long. 

Other  Amphibians  of  the  era  walked  on  all  fours.  Pigs. 
204,  204  a  represent  the  tracks  of  a  hind  foot  and  fore  foot 


REPTILIAN  AGE. 


187 


of  one  kind,  and  205,  205  a  those  of  another,  both  from  the 
Connecticut  valley. 


Figs.  203-206. 


206* 


Tracks  of  Amphibians  and  True  Reptiles. 


Amphibians :  Figs.  203,  203  a,  Otozoum  Moodii  (X  /'«) ;  204,  204  a,  Anisopus  Dewyanus  ( X  %) ;  205,  205  a, 
A.  gracilis  ( X  %).  —  True  Reptile:  Fig.  206,  206  a,  Anomcepus  scampus,  a  Dinosaur  ( X  J4). 

All  the  Amphibians,  there  is   reason  to  believe,  had  large 
teeth  and  scale-covered   bodies,  like   the   Amphibians   of  the] 
Carboniferous  age.      A  tooth  of  a  related  four-footed  species 
from   Europe  is    shown  two  thirds  the   natural   size   in   Pig. 
207.     The  head  of  the  Amphibian  that  was  thus  armed  was  ; 
over  2  feet  long,  and  three  fourths  as  broad. 

There  were  also  true  Eeptiles  of  various  kinds.  One  division 
of  them,  called  Dinosaurs  (meaning  terrible  lizards),  had  the 
hinder  feet  three-toed  like  those  of  birds.  The  tracks  of  one 
from  the  Connecticut  valley  sandstone  is  shown  one-sixth  the 
natural  size  in  Eig.  206.  They  .walked  usually  on  their  hind 


188  MESOZOIC  TIME. 


legs,  like  bipeds,  but  sometimes  put  their  forefeet  down.  These 
were  four-toed.  The  print  of  the  forefoot  of  this  species  is 
represented  in  Fig.  206  a. 

Fig.  207.  There  are  many  kinds  of  three-toed  tracks  in 

the  Connecticut  valley  sandstone  which  have 
never  been  found  associated  with  tracks  of  the 
forefeet;  and  as  they  have  precisely  the  form 
of  those  of  birds,  they  have  been  regarded  bird- 
tracks.  But  they  may  have  been  all  made  by 
these  bird-like  Eeptiles. 

Some  of  the  Dinosaurs  of  the  Jurassic  and 
Cretaceous  periods  better  deserve  the  name  of 
saurus.  terrible  lizards.     The  Megalosaur  was  a  huge 

carnivorous  reptile  25  to  30  feet  long;  the  Iguanodon  and 
Hadrosaurs  were  vegetable  eaters,  fully  as  large. 

Another  division  included  Enaliosaurs,  or  the  Sea-Saurians, 
which  had  paddles  like  whales,  and  were  12  to  50  feet  long. 


Fig.  208. 


Ichthyosaurus  communis  ( X  /,0o)- 
a,  one  of  the  vertebrae. 


One  kind,  called  Iclithyosaurs  (meaning  fish-lizards]  (Fig.  208), 
had  a  short  neck,  a  very  large  eye,  and  thin  vertebrae  concave 


REPTILIAN  AGE.  189 


on  both  sides  (Fig  208  a),  much  resembling  those  of  fishes. 
One  species  was  30  feet  long.  Another  kind,  called  Plesiosaurs 
(meaning,  somewhat  like  a  lizar d),  had  a  long  snake-like  neck 
(Fig.  209),  short  body,  and  vertebrae  as  long  as  broad. 

Fig.  209. 


Plesiosaurus  dolichodeirus  (  x  J60). 
a,  one  of  the  vertebrae  ;  b,  profile  of  same. 


A  third  division  included  the  Mosasaurs,  —  snake-like  rep- 
tiles, 15  to  80  feet  long,  with  short  paddles,  jaws  sometimes 
a  yard  long,  and  the  lower  jaw  peculiar  in  having  an  elbow- 
joint  to  fit  it  to  be  used  like  an  arm  for  working  the  carcass  > 
of  a  great  beast  down  its  enormous  throat.  They  had  power- 
ful teeth;  one  of  them,  about  half  the  size  of  the  largest,  is 
represented  in  Fig.  210.  Several  species  have  been  found  in 
the  Cretaceous  beds  of  New  Jersey  and  Kansas,  along  with 
Hadrosaurs,  Dinosaurs,  and  other  kinds. 

A  fourth  division  included  Crocodiles,  with  long  slender  jaws 
like  the  Gavial,  the  crocodile  of  the  Ganges. 


190 


MESOZOIC  TIME. 


Fig.  210. 


A.  ^h  division  included  flying  Beptiles, 
called  Pterosaurs  (from  the  Greek  for  winged 
Saurian).  One  of  them,  reduced  to  one 
fourth  the  natural  size,  is  represented  in  Fig. 
211.  The  wing  is  made  by  the  elongation 
of  one  of  the  fingers  and  the  expansion  of 
the  skin  from  the  side  of  the  body.  Some 
species  from  Kansas  had  an  expanse  of  wing 
of  24  or  25  feet.  They  had  the  habits  of  "] 
bats. 

Thus  the  age  was  literally  an  age  of 
Beptiles.  Air,  earth,  and  seas  were  all  occu- 
pied by  them,  and  by  species  of  great  mag- 
nitude, among  them  those  of  the  highest 
grade.  The  Eeptilian  type  thus  had  its 
maximum  display  in  Mesozoic  time. 

Birds.  —  A  bird  with  its  feathers  has  been  found  fossil  in 
the  Oolyte  of  Solenhofen,  Germany;  and  bones  of  a  number 
of  birds  in  the  Cretaceous  of  the  United  States.  The  Solen- 
hofen bird  had  a  long  tail,  furnished  with  a  row  of  long  quills 
either  side.  A  Kansas  species,  described  by  Professor  Marsh, 
had  teeth  set  in  sockets,  —  a  striking  Eeptilian  character. 

Mammals.  —  Bones  from  a  few  species  of  Mammals  have 
been  found,  the  earliest  in  the  Triassic  beds  of  Germany  and 
North  Carolina.  Fig.  212  represents  a  jaw-bone  from  North 
Carolina.  The  remains  of  other  related  kinds  have  been  found 


Tooth  of  a  Mosasaur. 


REPTILIAN  AGE.  191 


in  the  Oolyte  at  Stonesfield,  England,  and  also  in  the  Upper 
•Oolyte  in  the   Purbeck    beds.     The   species   are   Marsupials, 


Fig.  211. 


Pterosaur. 
Fig.  211,  Pterodactylus  crassirostris  (X  #). 

that  is,  mammals  related  to  the  Opossum  and  Kangaroo;  they 
are  peculiar  in  having  a  pouch  (Marsupium,  in  Latin)  on  the 
under  side  of  the  body,  over  the  breast  of  the  mother,  for 

Fig.  212. 


Dromatherium  sylvcstre. 


receiving  the  young,  which  are  born  in  an  immature  state. 
Nearly  all  modern  Marsupials  are  confined  to  the  continent  of 
Australia;  a  few  exist  still  in  America. 


192  MESOZOIC  TIME. 


Thus  all  the  classes  of  Yertebrates  had,  in  Mesozoic  time, 
their  species,  even  to  Birds  and  Mammals.  As  early  as  the 
/  Triassic,  its  first  period,  the  Amphibians  passed  their  climax 
\  in  numbers,  size,  and  grade,  little  being  afterward  known  of 
nhe  huge  scale-covered  tribe ;  and  during  its  following  periods 
true  Reptiles  had  their  time  of  greatest  expansion,  giving  a 
strong  Reptilian  character  to  the  Reptilian  age.  But  the 
Birds  and  Mammals  which  appeared  in  the  age  were  only  the 
commencement  of  tribes  that  were  to  reach  their  fullest  dis- 
play in  later  time.  Both  the  early  Birds  and  Mammals  had 
marks  of  inferiority,  and  also  characteristics  that  showed  some 
relation  to  the  Reptiles  with  which  they  lived.  Thus  the 
Birds  had  long  tails,  and  some,  at  least,  true  teeth  like  Rep- 
tiles ;  and  the  Mammals  have  been  called  semi-oviparous,  that 
is,  kinds  whose  young  were  in  an  immature  state  when  born, 
approximating  in  this  respect  to  the  egg  state,  which  is  an 
example  of  an  extreme  degree  of  immaturity.  It  is  also  a 
fact  of  interest  that  among  Reptiles  the  Dinosaurs  were  like 
birds,  not  only  in  their  biped  mode  of  locomotion,  but  in  the 
special  way  by  which  they  were  adapted  to  this  kind  of  pro- 
gression ;  for  they  had  the  same  kind  of  feet  as  birds,  the 
same  number  of  toes,  the  same  number  of  joints  to  the  sev- 
eral toes,  also  hollow  bones  in  part,  a  somewhat  similar 
structure  in  the  hinder  part  of  the  skeleton  to  which  the  leg- 
^  bones  are  articulated,  and  other  points  of  resemblance. 

The  progress  in  the  life  of  the  world  in  Mesozoic  time  is 


REPTILIAN  AGE.  193 


also  seen  in  the  fact,  that  with  the  opening  of  its  third  period, 
Sharks  and  Ganoids  were  no  longer  the  only  fishes,  the  mod- 
ern tribes  having  made  their  appearance;  and,  too,  Conifers, 
Tree-ferns,  and  Cycads  were  not  the  only  forest-trees,  for  al- 
ready Palms  and  Aagbspesas  had  added  vastly  to  the  variety  fix 
of  foliage  and  to  the  richness  of  the  flowers  and  fruits.  Of 
lines  of  transition  from  the  older  trees  up  to  these  Palms  and 
AngiagpfTTVi"  nothing  is  known.  ^ 

The  old  law  of  change  characterized  the  life  of  Mesozoic 
time.  New  fossils  are  found  in  every  successive  rock-stratum, 
and  also  older  kinds  are  missed.  The  system  of  life  was  in 
course  of  expansion  by  the  introduction  of  new  species  and  a 
casting  off  of  the  old. 

3.    Mountain-making  in  Mesozoic  Time. 

The   Sierra  Nevada,  Wahsatch,  and   some   other  ranges  of  [ 
the  western  slope  of  the  Eocky  Mountains  were  made  at  the 
close  of  the  Jurassic.     All  the  strata  there  existing  from  the 
bottom  of  the  Silurian  to  the  top  of  the  Jurassic  were  folded) 
up  in  the  making  of  the  Wahsatch  Mountains,  and  probably  ) 
in  that  of  the  Sierra  Nevada. 

In  the  course  of  the  Jurassic,  or  at  its  close,  the  Triassic 
(or  Triassic  and  Jurassic)  rocks  of  the  Atlantic  border  (Con- 
necticut Eiver  valley  and  elsewhere)  were  slowly  tilted;  and 
then  occurred  a  great  number  of  deep  fractures,  mostly  par- 
allel in  course  to  the  direction  of  the  areas  of  the  sandstone, 

9  M 


194  CENOZOIC  TIME. 


which  opened  down  to  a  region  of  liquid  rock;  for  the  liquid 
rock  came  to  the  surface  and  cooled,  and  now  constitutes 
many  ridges,  such  as  Mount  Holyoke,  Mount  Tom,  the  Pali- 
sades on  the  Hudson,  and  others  between  Nova  Scotia  on 
the  north  and  South  Carolina.  During  the  formation  of  the 
sandstone  a  slow  sinking  was  in  progress,  as  is  proved  by  the 
footprints  on  the  surfaces  of  layers  and  other  markings,  these 
showing  that  the  layers  —  originally  mud-flats  and  sand-flats 
of  an  estuary  —  were  successively  at  the  water-level.  The 
sinking  brought  a  strain  on  the  rock-made  bottom  of  the 
trough,  and  ended  in  a  breaking  of  the  crust,  and  thence 
came  the  ejections  of  trap.  The  trap  resembles  the  cooled 
rock  of  most  volcanoes,  but  is  commonly  much  more  compact. 

IV.  — Oenozoic  Time. 

CENOZOIC  TIME  comprises  two  Ages :  — 
I.  The  TERTIARY,  or  AGE  OF  MAMMALS. 

II.    The    QUATERNARY,    OT   AGE   OF   MAN. 

I.   The  Tertiary,  or  Age  of  Mammals. 

The  Tertiary  age  has  been  divided  into  three  sections:  (1) 
the  EOCENE;  (2)  the  MIOCENE;  (3)  the  PLIOCENE.  These 
terms  signify,  severally,  (1)  the  dawn  of  recent  time;  (2)  the 
less  recent ;  (3)  the  more  recent.  The  areas  of  Tertiary  rocks 
in  North  America  and  England  are  distinguished  on  the  maps, 


TERTIARY  AGE. 


195 


pages  105  and  114,  by  being  lined  from  the  left  above  to 
to  the  right  below. 

1.   Rocks. 

In  the  accompanying  map   the  white    area   represents  the 
dry  land  of  the  continent  in  the  Eocene,  or  early  part  of  the 

Fig.  213. 


Hap  of  North  America  in  the  early  part  of  the  Tertiary  Period. 

Tertiary.  Only  the  borders  of  the  Atlantic,  the  Gulf  of 
Mexico,  and  the  Pacific  (the  shaded  portions)  were  covered 
by  the  sea,  and  over  these  parts  Tertiary  rocks  were  forming 
through  marine  action  aided  by  the  contributions  of  rivers. 


196  CENOZOIC  TIME. 


The  geographical  changes  since  the  opening  of  the  Creta- 
ceous period  were  great,  as  will  be  seen  by  comparing  the 
map  with  that  on  page  177.  The  Eocky  Mountain  region 
was  now  above  the  sea.  The  rivers  of  the  eastern  part  of 
the  continent,  or  those  contributing  waters  and  sediment  to 
the  Atlantic,  had  two  thirds  or  more  of  their  present  extent; 
but  the  Ohio  and  Mississippi  were  still  independent  streams, 
emptying  together  into  an  arm  of  the  Mexican  Gulf.  The 
Missouri  and  other  western  streams  were  just  beginning  to 
be.  The  Mountain  region  but  slowly  emerged,  and  till  near 
the  close  of  the  Tertiary  there  were  great  lakes  instead  of 
great  rivers.  In  the  Eocene  the  lakes  occupied  the  Green 
River  and  other  summit  basins.  Afterward  they  were  farther 
east  and  west,  and  in  the  Pliocene,  as  Marsh  states,  a  lake 
extended  from  Northern  Nebraska  to  Texas.  The  Tertiary 
consequently  includes,  from  its  beginning,  vast  fresh-water  as 
well  as  marine  formations. 

Marine  Tertiary  beds  of  the  Eocene  period  were  formed  on 

the  Atlantic  border  south  of  New  York,  and  on  the  borders 

of  the  Mexican  Gulf;  but  Miocene  only  on  the  Atlantic  bor- 

|    der,  some   change    of   level   having    excluded   them   from   the 

Gulf  border  west   of  Florida;   and  Pliocene   along   the   coast 

-^(   region  of  South  Carolina,  though  of  this  there  is  doubt.     On 

the  Pacific  border  there-  are  marine  beds,  both  of  the  Eocene 

and  Miocene  periods;  the  latter  are  most  extensive. 

Underneath  the  Marine  Eocene  beds  of  the  Lower  Mississippi 


TERTIARY  AGE.  197 


there  are  Lignitic  beds,  that  is,  beds  containing  lignite  — 
a  kind  of  mineral  coal  retaining  usually  something  of  the 
structure  of  the  original  wood  —  alternating  with  beds  that 
are  partly  marine,  the  whole  indicating  that  fresh-water  marshes 
there  alternated  with  fresh- water  lakes  and  salt  seas ;  for  the 
Lignitic  beds  were  once  beds  of  vegetable  debris  such  as  are 
formed  in  marshes. 

Fresh-water  Tertiary  beds  cover  large  areas  over  the  Eocky 
Mountain  summit  region,  and  its  eastern  slope,  as  well  as 
part  of  its  western  in  Oregon  and  elsewhere.  They  were 
formed  in  and  about  the  great  lakes  alluded  to  above.  Im- 
mense numbers  of  bones  of  mammals  and  many  entire  skele- 
tons are  contained  in  these  beds,  showing  that  the  shores  of 
these  lakes  were  the  resort  of  wild  beasts,  some  of  them  of 
elephantine  size.  In  the  Green  River  basin  and  other  parts 
of  the  summit  region  the  beds  are  Eocene;  while  over  the 
eastern  slope  they  are  mostly  Miocene  and  Pliocene,  the 
latter  of  widest  extent. 

Underneath  these  fresh-water  beds  over  the  eastern  slope 
in  the  region  of  the  Upper  Missouri,  and  far  north  in  British 
America,  as  well  as  far  south,  there  is  a  Lignitic  formation 
which  is  partly,  especially  below,  of  brackish- water  origin; 
and  these  are  equivalents  of  the  Lignitic  beds  below  the 
marine  Eocene  of  Mississippi.  Over  the  summit  region  of 
the  mountains  the  Lignitic  formation  has  a  thickness  of  sev- 
eral thousand  feet,  and  instead  of  Lignitic  beds  there  are  val- 


198  CENOZOIC  TIME. 


uable  beds  of  mineral  coal.  There  are  marine,  brackish-water, 
;  and  fresh-water  strata  in  the  formation,  the  latter  mainly  in 
the  upper  part.  The  coal-beds  occur  in  Wyoming,  Utah,  and 
Colorado,  and  some  of  them,  opened  near  the  Pacific  Bailroad, 
afford  coal  for  its  locomotives.  These  beds  overlie  the  Cre- 
taceous beds  conformably,  and  the  latter  also  have  similar  coal- 
beds;  so  that  the  Cretaceous  deposits  and  era  here  blend  with 
the  Tertiary.  Moreover,  a  very  few  Cretaceous  shells  occur  in 
some  of  the  marine  beds  and  the  remains  of  some  reptiles 
related  to  the  Cretaceous  Dinosaurs.  The  great  majority  of 
the  fossils  are  Tertiary  in  aspect  and  genera,  and  they  are 
therefore  here  referred  to  the  Eocene,  although  regarded  as 
Cretaceous  by  some  geologists.  These  Lignitic  beds  and  the 
.  underlying  Cretaceous  were  all  upturned  together  in  one 

-  /   mountain-making   effort,  before   the   fresh-water  Eocene 

A" 

i  of  the  Green  Eiver  basin  were  deposited. 

In  Great  Britain  there  are  marine  Eocene  Tertiary  beds  in 
the  "  London  basin,"  and  next  a  thin  Pliocene  stratum,  no  ma- 
rine Miocene  existing  there.  Over  Europe  and  Asia  the  Eocene 
formation  was  widely  distributed,  showing  that  those  continents, 
even  as  late  as  the  early  Tertiary,  were  largely  under  the 
sea.  The  Pyrenees,  portions  of  the  Alps,  Apennines,  Carpa- 
thians, and  mountains  in  Asia  were  partly  made  of  them. 
The  beds  in  many  places  contain  the  coin-shaped  foraminifers 
(Ehizopod  shells)  called  Nummulites,  varying  from  half  an 
inch  to  one  inch  or  more  in  diameter;  and  the  limestone  of 


TERTIARY  AGE.  199 


which   some  of  the  Egyptian  pyramids  are  built  is  made  up 
chiefly  of  Nummulites.     One  of  them  is  shown  in  Fig.  214; 
the  exterior  is  represented  as  removed  from  part        Figt 
of  the  interior  to  show  the  cells,  which  were  once 
occupied  by  the  minute  BMzopods.     Some  species 
of   a   related  genus  occur   in  modern  coral  seas. 
They  must  have  been  exceedingly  abundant  over 
the  great  continental  seas  of  the  Tertiary.     Miocene  beds  have 
a  thickness   of  several   thousand   feet  in   Switzerland    (consti- 
tuting the  Eigi  and  some  other  summits),  and  occur  in  many  ( 
other   parts  of   Europe;    but   they  are   limited  in   area   com-  } 
pared  with   the  Eocene.      Marine  Pliocene   beds   are  of  still 
less  extent,  yet  have  a  thickness  in  Sicily  of  3,000  feet. 

The  marine  Tertiary  rocks  are  very  various  in  kind.     The 
larger   part   are  soft   sand-beds,  clay-beds,  and  shell  deposits, 
the   shells  often  looking  nearly  as  fresh  as  those  of  a  mod- 
ern  beach.      Others    are    moderately   firm    sandstone.      There 
are    also  loose  and  firm  limestones.      The   green  sand   called* 
"marl/''   used  as   a   fertilizer,   which    is    so    characteristic   of^ 
the  Cretaceous,  also  constitutes  beds  in  the  Tertiary  of  New 
Jersey. 

The  fresh-water  beds  are  like  the  softer  marine  beds, 
but  contain,  of  course,  no  marine  shells.  Part  of  them  are 
quite  firm;  but  others  are  easily  worn  by  the  rains.  Some 
great  areas  in  the  Eocky  Mountain  region,  both  over  the 
summit  and  the  eastern  slope,  have  been  reduced  in  this  way 


200  CENOZOIC  TIME. 


to  areas  of  isolated  ridges,  towers,  pinnacles,  and  table-topped 
hills,  that  are  mostly  barren,  owing  to  the  dry  climate,  and 
which  are  therefore  called  "  Bad  Lands,"  or  in  French  (in 
which  language  the  expression  was  first  applied),  "  Mauvaises 

Terres." 

2.  Life. 

The  life  of  the  Tertiary  age  shows  in  all  its  tribes  an  ap- 
proximation to  that  of  the  present  time.  The  mammals,  and 
probably  the  birds,  are  all  of  extinct  species.  But  among 
the  plants  and  the  lower  orders  of  animals  there  were  many 
species  that  still  exist :  in  the  Eocene,  a  small  percentage ;  in 
the  Miocene,  25  to  40  per  cent;  and  in  the  Pliocene,  a  much 
larger  proportion.  The  common  oyster  and  clam  were  living 
as  far  back  as  the  Miocene  era,  along  with  a  large  number 
of  shells  that  are  now  extinct  species.  Progress  through  the 
Tertiary  era  was  gradual  in  all  departments. 

The  forests  of  North  America  were  much  like  the  modern, 
but  with  a  larger  proportion  of  warm-climate  forms.  Palms 
flourished  over  Europe  and  in  England  through  the  Eocene. 
In  the  Miocene  the  European  species  were  still  those  of  a 
warmer  climate  than  the  present,  and  included  some  Australian 
species.  Even  in  the  Arctic  zone  there  were  in  the  Miocene 
great  forests  of  Beach,  Oak,  Poplars,  Walnut,  and  Redwood 
(Sequoia,  the  genus  to  which  the  "  great  trees  "  of  California 
belong),  with  Magnolias,  Alders,  and  others. 

The   modern   aspect  of  the   marine   shells   is   shown  in  the 


TERTIARY  AGE. 


201 


following  figures :   Figs.  215  -  219,  of  American  Eocene   spe- 
cies,  and   220  -  223,   of  Miocene  from    the    Atlantic   border. 

Figs.  215-219. 


Eocene  of  Alabama. 

Fig.  215,  Ostrea  sellaeformis  ;  216,  Crassatella  alta ;  217,  Astarte  Conradi ;  218,  Cardita  planicosta ;  219, 
Turritella  carinata. 

This  is  further  manifest  in  the  following  figures  of  fresh-water 
shells  from  the  Lignitic  beds  of  the  Rocky  Mountain  regions, 

Figs.  220-223. 

222 


Miocene  of  Virginia. 
Figs.  220,  221,  Crepidula  costata ;  222,  Yoldia  limatula ;  223,  Callista  Sayana. 

9* 


202 


CENOZOIC  TIME. 


—  species  which  are  supposed  to  prove  that   those  beds   are 
Tertiary  instead  of  Cretaceous.     To  appreciate  the  change  since 


Fig.  230. 


Shells  of  the  Lignitic  Beds. 

Lamellibranchs  :  Figs.  224,  224  a,  Corbula  mactriformis ;   225,  Cyrene  intermedia ;  226,  Unio  priscus.  — 
Gasteropoda  :  Fig.  227,  Viviparus  retusus ;  228,  Melania  Nebrascensis ;  229,  Viviparus  Leai. 

Paleozoic  time,  the  reader  should  turn  back  to  the  figures  of 

shells  on  pages  121  to  133. 

The  Tertiary  Vertebrates  were  more  unlike  the  moderns 
than-  the  Invertebrates.  Among 
fishes,  Sharks  were  exceedingly 
abundant,  and  their  teeth,  the  most 
enduring  part  of  the  skeleton,  are 
very  common  in  some  of  the  beds; 
and  those  of  one  kind,  pointed,  tri- 
angular in  form,  were  nearly  as 
large  as  a  man's  hand.  One  of 
the  smaller  of  these  teeth  is  repre- 
sented in  Fig.  230. 

The  true  Eeptiles  were  Crocodiles, 

Lizards,  Snakes,  gigantic  and  smaller  Turtles,  and  others. 


Shark's  tooth. 

Carcharodon  angustidens. 


TERTIARY  AGE. 


203 


Among  the  birds  there  were  Owls,  Woodpeckers,  Cormo- 
rants, Eagles;  and  those  of  France  included  Parrots,  Trogons, 
Flamingoes,  Cranes,  Pelicans,  Ibises,  and  other  kinds  related 
to  those  of  warm  climates. 

The  Mammals  of  Mesozoic  time,  thus  far  discovered,  were 
probably  all  of  the  lower  order  called  Marsupials;  but  with 
the  opening  of  the  Cenozoic  era  there  were  true  Mammals. 
The  Eocene  beds  about  Paris,  France,  afforded  to  Cuvier  the 
first  specimens  described ;  and  now  they  are  known  from  all 
parts  of  the  world,  and  from  none  in  greater  variety  than  from 
the  fresh-water  Tertiary  region  west  of  the  Mississippi. 

The   earliest   kinds    were   related   most  nearly  to  the  mod- 


Fig.  281. 


Tapirus  Indicus,  the  modern  Tapir  of  India. 


ern  Tapir  (Fig.  231),  Hog,  Ehinoceros,  and  Hippopotamus. 
There  were  also  kinds  between  these  and  the  Deer.  All  the 
above  mentioned  are  Herbivores,  that  is,  plant-eaters.  There 


204 


CENOZOIC  TIME. 


were  also   Carnivores,  or  flesh-eaters,  related  to  the  dog  and 
wolf,  and  Monkeys  related  to  the  Lemurs. 

One  of  the  Herbivores  of  the  Bocky  Mountain  Eocene  is 
the  Dinoceras  of  Marsh,  —  a  figure  of  the  skull  of  which  is 
here  given.  It  was  nearly  as  large  as  an  Elephant,  but  had 

Fig.  232. 


Dinoceras  mirabile  (X  %). 


six  horns  and  was  somewhat  related  to  the  Ehinoceros.  Fig. 
233  represents  the  skull  of  one  of  the  Miocene  species,  — 
an  Oreodon,  —  which  was  intermediate  in  characters  between 
/  the  Deer,  Camel,  and  Hog.  The  form  of  a  European  spe- 
cies more  like  a  Deer,  called  a  XijpJwdon,  is  given,  as  re- 
stored by  Cuvier,  in  Fig.  234.  There  were  also  Horses 
through  the  Tertiary;  but  while  the  modern  Horse  has  only 


TERTIARY  AGE. 


205 


one  toe  out  of  the  full  mammalian  number  five,  some  of  the 
Pliocene  had  three  toes,  one  large,  and  two  too  short  for  use; 

Fig.  233. 


Oreodon  gracilis. 

Miocene  kinds  had  three  toes,  and  all  usable;  and  the  Eocene 
had  four  toes,  and  all  usable. 

Fig.  234. 


Xiphodon  gracile. 


206  CENOZOIC  TIME. 


In  the  Miocene  and  Pliocene  there  were  Mastodons,  Ele- 
phants, Bhinoceroses,  Camels,  and  Monkeys  over  the  Bocky 
Mountain  region,  besides  many  smaller  species.  The  marine 
Tertiary  of  the  Atlantic  border  has  afforded,  as  should  be 

r  expected,  but  few  of  these  species.     Cattle  related  to  the  Ox 
have  not  been  found  in  beds  earlier  than  the  Pliocene. 

The   Mammalian   type  was  at   last   extensively  unfolded,  its 
grand  divisions   being  well  represented.      But  the  maximum 
,     /  display  of  the  brute  races  took  place  still  later,  in  the  early 
\  or  middle  Quaternary,  after  Man  had  appeared. 

3.    Mountain-making. 

/  In  North  America,  after  the  deposition  of  the  coal  (or  Lig- 
)  nitic)  beds  of  the   summit  region  of  the  Bocky   Mountains, 
{  /    and   of  similar  beds   in  California,  there  was   a   flexing   and 
/    upturning  of  the   strata  along  with  those   of  the   Cretaceous 
'    beneath,  —  which  together,  as  has  been  stated,  make  one  con- 
)    tinuous  series,  —  and  ridges  over   3,000   feet  and  more  high 
V     were  thus  made  in  the  coast  region  of  California,  and  others 
of  greater  height  in  Mexico,  New  Mexico,  Colorado,  and  to 
the  north. 

During  the  formation  of  the  Lignitic  beds  the  uplifting  of 
the  whole  Bocky  Mountain  region  above  the  sea  was  in  pro- 
gress; for  such  beds  of  vegetable  debris  as  they  were  made 
from  show  that  long  periods  of  rest  above  the  sea  alternated 
with  shorter  periods  of  submergence.  After  the  epoch  of  up- 


TERTIARY  AGE.  207 


turning  which  followed,  if  not  also  contemporaneously  with 
it,  this  elevation  was  continued,  and  without  a  return  again 
below  the  sea-level.  But  the  existence  of  the  vast  fresh-water 
lakes  over  the  surface  proves,  as  first  observed  by  Hayden, 
that  the  rising  went  forward  with  extreme  slowness,  and 
probably  with  long  delays  at  intervals;  and  it  is  quite  cer- 
tain that  the  present  height  —  at  least  10,000  feet  in  Colo- 
rado and  Wyoming  above  the  level  in  Cretaceous  times,  since 
the  Cretaceous  beds,  full  of  marine  fossils,  are  now  at  this 
height  —  was  not  attained  before  the  close  of  the  Pliocene, 
if  it  was  then. 

The  Pyrenees,  Apennines,  part  of  the  Northern  Alps,  and 
other  high  mountains  of  Switzerland,  the  Carpathians,  and 
other  mountains  in  Eastern  Europe  were  raised  thousands  of 
feet,  and  the  mountain  regions  in  Western  Thibet,  in  Asia, 
16,500  feet,  after  the  Eocene  Tertiary  had  partly  passed,  and 
the  rise  perhaps  began  at  the  same  time  with  that  of  the  ^ 
Cretaceous  and  Lignitic  mountains  of  the  Rocky  Mountain 
summit  and  the  coast  region  of  California. 

After  the  Miocene  another  range  2,000  to  3,000  feet  in 
height  was  made  along  the  California  coast-region  west  of  the 
Cretaceous  range,  and  some  disturbances  took  place  in  the 
Tertiary  over  the  summit  region  of  the  Rocky  Mountains. 

The  close  of  the  Miocene  was  a  time  of  great   disturbance 
and  of  mountain-making  also  in  Europe,  to  the  north  of  the  j 
Alps,  in  Switzerland,  and  elsewhere. 


208  CENOZOIC  TIME. 


At  the  same  time,  that  is,  in  the  Miocene  era,  great  erup- 
tions of  igneous  rocks  took  place  over  the  western  slope  of 
the   Rocky   Mountains,   covering   thousands   of   square   miles; 
^-.^  and  probably  the  deep  fractures  were  then  opened  which  gave 
/     origin  to  the  volcanoes  Mount  Shasta,  Mount  Hood,  and  other 
summits  in  the  Cascade  Range.     So  also  along  the  coast  of 
(  Ireland  and  of  Scotland,  and  the  Inner  Hebrides  to  the  Faroe 
/    Islands,  the  eruptions  were  of  great  extent.     Fingal's  Cave  and 
S    the  Giant' s  Causeway  date  from  this  period. 

In  each  case  over  the  Rocky  Mountains  the  making  of  a 
mountain  range  was  preceded,  as  in  that  of  the  Appalachian 
region  (page  168),  by  a  sinking  of  the  earth's  crust  where  the 
range  was  to  be,  and  the  accumulation  in  the  trough,  as  it 
formed,  of  some  thousands  of  feet  of  deposits.  Then  followed 
the  catastrophe,  —  as  explained  for  the  Appalachian  region  on 
page  172,  —  causing  upturnings,  foldings,  fractures,  consolida- 
tion; and  sometimes  also  a  crystallization  of  the  beds,  chang- 
ing them  to  granite,  gneiss,  and  allied  rocks.  Each  time,  after 
a  mountain  system  was  completed,  that  part  of  the  earth's 
crust  was  too  much  stiffened  to  be  the  site  of  another  sink- 
ing trough,  and  consequently  the  trough  made  later,  if  there 
was  any  so  made,  was  to  one  side  of  the  former.  In  the 
Tertiary  the  crust  over  the  whole  Rocky  Mountain  region  had 
finally  become  so  stiffened  that  no  new  trough  was  begun 
after  the  Miocene;  and  instead  of  a  folding  of  the  thick  Mio- 
cene formation  into  a  mountain  range,  great  breaks  of  the 


QUATERNARY  AGE.  209 

crust  took  place  from  which  floods  of  lavas  were  let  loose  and 
the  lofty  volcanoes  were  begun. 

4.    Climate. 

During  Mesozoic  time  the  Arctic  zone  was  warm  enough 
for  great  Reptiles, —  warm-climate  species,  —  and  the  British 
seas  for  coral-reefs. 

The  close  of  the  Cretaceous  was  probably  an  era  of  unusual- 
cold,  sending  cold  oceanic  currents  from  the  Arctic  zone;  for 
no  other  cause  will  account  for  the  general  destruction  of  spe- 
cies  that  then  took  place  over  the  continental  seas  of  America, 
Europe,   and  Asia.     But  the  Eocene   era  was   one   of   warm 
climate  again  over  Great  Britain,  —  for  England  was  then  a 
land  of  Palms;   and  Palms  continued  to  flourish  over  Middle 
and  Southern  Europe  during  the  Miocene  period.      Through 
both  the  Eocene  and  Miocene  the  Arctic  lands  were  covered 
with  forests,  and  hence  the  Arctic   climate  must  have  been 
comparatively   warm,  —  not  colder  at    least    than  the  presents 
climate  of  the  Middle   United   States-  and  Northern  Prussia.]' 
There  was  a  cooling  off  with  the  progress   of  the  Miocene, 
and  by  the  close  of  the  Tertiary  the  earth  had  probably  its   j 
frigid,  temperate,  and  torrid  zones,  nearly  as  now. 

2.   Quaternary  Age,  or  Era  of  Man. 

The  scene  of  work  for  the  Quaternary  age  was  to  a  large 
extent  widely  different  from  that  of  the  Tertiary  and  preceding 


210  CENOZOIC  TIME. 


ages;  and  the  kind  of  work  was  equally  different.  With  the 
close  of  the  Tertiary  the  continent,  which  was  begun  in  the 
nucleal  V  of  Archsean  time,  was  finished  out  very  nearly  to 
its  present  limits,  and  at  its  close  an  elevation  added  the  Ter- 
tiary formation  of  the  sea-border  to  the  dry  land. 

This  accomplished,  the  Quaternary  opened.  Agencies  were 
now  at  work  over  the  broad  surface  of  the  continent  —  its 
dry  land,  and  not  continental  seas,  as  formerly  —  transport- 
ing southward  gravel  and  earth  from  regions  to  the  north,  in 
order  to  cover  the  hills  with  gravel  and  soil  and  fill  the  val- 
leys with  alluvial  plains.  Over  both  Europe  and  America 
transportation  went  forward  from  the  high  latitudes  southward, 
except  where  there  were  mountains  sufficiently  lofty  to  be 
sources  of  independent  movements.  Hills  and  valleys  were 
no  impediment  to  the  great  agent  engaged  in  this  immense 
continental  system  of  transportation.  The  aid  of  the  ocean 
was  not  needed  in  these  movements,  and  was  not  given  ex- 
cept to  a  small  extent  along  its  borders. 

After  these  great  results  were  attained  the  work  of  the 
rivers  went  on  more  quietly,  and  finally,  through  this  and 
other  agencies,  in  connection  with  some  change  of  continental 
level,  the  earth  assumed  slowly  its  present  perfected  condition 
of  surface  and  climate. 

The  age  is  divided  into  three  periods :  —  (1)  the  GLACIAL 
period;  (2)  the  CHAMPLAIN  period;  (3)  the  BECENT  or  TEE- 
RACE  period. 


QUATERNARY  AGE.  —  GLACIAL  PERIOD. 


1.  Glacial  Period. 

1.  Glacial  Phenomena.  —  The  general  facts  are  these:  — 
In  America  and  Europe,  over  the  northern  latitudes,  sand, 
gravel,  stones,  and  masses  of  rock  hundreds  of  tons  in  weight 
are  found  from  a  few  miles  to  a  hundred  and  more  south  of 
the  region  whence  they  were  derived.  This  transported  ma- 
terial is  called  drift,  and  the  stones  or  rocks,  bowlders. 

In  North  America,  the  region  over  which  the  transportation 
took  place  embraced  the  whole  surface  from  Labrador  or 
Newfoundland  to  the  western  borders  of  Iowa,  and  farther 
west  for  a  distance  not  yet  determined,  and  it  reached  south- 
ward to  the  parallel  of  40°  and  in  some  places  beyond  this. 
In  Europe  it  included  the  British  Islands  and  Northern  Eu- 
rope, down  to  the  parallel  of  50°,  where  the  temperature  is 
about  the  same  as  along  the  parallel  of  40°  in  North  America. 
The  direction  of  travel  was  generally  to  the  southeastward, 
southward,  or  southwestward. 

-    The  fact  and  the  direction  of  transportation  have  been  as- 
certained by  tracing  the  stones  to  the  ledges  from  which  they 

were  derived.     Thus  bowlders  of  trap  and  red  sandstone  from  \ 

i 
the  Connecticut  valley  are  found  on  Long  Island,  and  masses  5 

of  granite,  gneiss,   quartzyte,  and   other   rocks  in  New  Eng-  < 
land,  to  the  southward  or   southeastward   of  the   ledges   that  > 
afforded  them.     In  the  same  manner  masses  of  granular  mar- 
ble have  been  proved  to  have  come  from  a  formation  50  or  7 


212 


CENOZOIC  TIME. 


100  miles  to  the  northward  of  their  present  position.  So 
again  masses  of  native  copper  are  found  in  Indiana  and  Illi- 
nois that  were  brought  from  the  veins  of  native  copper  south 
of  Lake  Superior.  The  greatest  distance  to  which  bowlders 
have  been  traced  has  been  400  or  500  miles  in  Europe,  200 
or  300  over  Eastern  North  America,  and  1,000  miles  along  the 
Mississippi  Eiver  valley,  where  they  reach  nearly  to  the  Gulf. 

The  masses  sometimes  contain  2,000  to  3,000  cubic  feet, 
so  that  they  compare  well  in  size  with  large  houses. 

Drift  regions  are  also  regions  of  extensive  planings,  pol- 
ishings,  and  scratchings  of  the  rocks  (Fig.  235).  These 

Fig.  235. 


Drift  scratches  and  planings. 


scratches  may  almost  anywhere  be  found  on  rocks  that  have 
been  recently  uncovered.  Yast  areas  are  thus  scoured  and 
scratched  over,  and  the  scratches  have  great  uniformity  in 
direction.  The  bowlders  also  are  scratched. 


QUATERNARY  AGE.  — GLACIAL  PERIOD.  213 

Scratches  and  bowlders  occur  on  top  of  Mount  Mansfield, 
the  highest  point  in  the  Green  Mountains,  4,430  feet  above  1 
the  sea,  and  at  a  level  of  5,500  feet  on  the  White  Mountains  5 
in  New  Hampshire;   and  the  direction  of  the  scratches  shows 
that  the  transporting   agent   moved  over   both  of  these   sum-  . 
mits   without   finding    in   them    any   serious    impediment,   and  M- — 
thence  continued  on  its  way  southeastward. 

The  drift  covers  the  mountains  and  hills  of  drift  regions, 
and  makes  also  a  large  part  of  the  formations  in  the  valleys. 
Over  the  hills  it  is  unstratified  drift)  the  sands,  gravel,  and 
stones  having  gone  down  pell-mell  together ;  in  the  ^valleys  it  )  ^ 
is  stratified  drift,  —  stratified  because  there  the  sands  and 
gravel  were  deposited  in  flowing  water,  which  sorted  some- 
what the  material  and  spread  it  out  in  beds.  The  excava- 
tions in  cities  or  villages  for  the  cellars  of  houses  are  often 
made  in  the  stratified  drift,  and  the  sands  usually  show  a 
succession  of  beds  which  is  evidence  of  the  action  of  water. 

2.  Cause  of  the  Glacial  Phenomena.  —  No  known  agent  is 
adequate  for  transportation  on  so  vast  a  scale  excepting  mov- 
ing ice.  And,  as  Agassiz  was  the  first  to  appreciate,  it  was 
glacier  ice.  The  size  of  the  blocks  transported  is  no  greater 
than  is  now  borne  along  on  the  backs  of  glaciers;  and  the 
planing  and  scratching  is  just  what  the  Alps  everywhere  ex- 
emplifies. The  moraines  of  the  glaciers,  as  explained  on  page 
60,  are  derived  in  the  Alps  from  the  cliffs  either  side  of  the 
ice-stream,  and  a  small  part  only  are  taken  up  by  the  abrad- 


214  CENOZOIC  TIME. 


ing  surface  at  bottom.  In  the  Continental  glacier  of  the  Gla- 
cial period,  the  stones,  gravel,  and  sand  were  gathered  from 
the  hills  over  which  the  ice  moved,  for  there  were  no  cliffs 
or  peaks  projecting  above  the  surface  even  in  hilly  New 
England.  The  White  Mountains,  as  above  stated,  have 
scratches  to  a  height  of  5,500  feet,  or  to  within  800  feet  of 
the  summit,  and  therefore  were  buried  in  the  great  glacier 
nearly  to  its  top,  and  in  snow,  if  not  ice,  for  the  rest.  Tak- 
I  ing  the  height  at  the  White  Mountains  as  a  guide,  the  upper 
surface  of  the  glacier  at  that  point  was  at  least  6,000  feet 
above  the  sea-level,  and  the  thickness  of  the  mass  about  5,000 
feet.  Prom  this  region  it  sloped  away  over  Southern  and 
Southeastern  New  England  to  its  place  of  discharge  in  the 
Atlantic.  A  thickness  of  even  2,000  feet,  which  is  over  four 
times  that  of  the  largest  Alpine  glacier,  would  have  given  great 
abrading  power  to  the  heavy  mass.  All  soft  or  decomposed 
rocks  would  have  been  deeply  worn  away  by  it,  and  hard 
rocks  with  open  joints  or  planes  of  fracture  torn  to  pieces; 
and  the  heavily  pressing,  slowly  moving  mass  would  have  taken 
the  loose  and  loosened  rock-material  over  the  hills  beneath 
into  itself,  as  additional  freight  for  transportation. 
/  Masses  of  trap  500  to  JLOOCLtons  in  weight  lie  along  the 
\  elevated  western  border  of  the  plain  of  New  Haven  in  Con- 
necticut, which  were  gathered  up  from  the  trap  hills  between 
Meriden  and  Mount  Tom  in  Massachusetts.  The  hills  are 
1,000  to  1,300  feet  high,  and  their  tops,  when  the  masses 


QUATERNARY  AGE.  — GLACIAL  PERIOD.  215 

were  taken  up,  were  1,500  to  2,000  feet  below  the  upper  sur- 
face of  the  overlying  glacier. 

A  glacier  moves  in  the  direction  of  the  slope  of  its  upper  ( 
surface,  in  spite  of  the  slope  of  the  surface  beneath  it.  It 
is  like  thick  pitch  in  this  respect.  If  pitch  were  dropped 
indefinitely  over  a  spot  in  a  plain,  it  would  spread  away 
indefinitely;  and  if  the  surface  around  had  a  rising  slope,  it 
would  fill  up  the  basin  and  then  keep  on  its  course.  So  it 
is  with  the  ice  of  a  glacier.  In  order  to  have  a  southeast- 
ward course,  a  glacier  must  have  its  surface  highest  to  the 
northwestward  with  slope  southeastward;  and  if  the  snows 
were  more  abundant  to  the  north  in  the  Glacial  era,  and  the 
melting  less  abundant  there,  than  to  the  south,  an  accumula- 
tion to  the  north  might  have  gone  on  that  would  have  pro- 
duced movement  southward.  If  the  plain  beneath  the  pitch 
had  deep  channels  obliquely  crossing  it,  the  pitch  in  these 
channels  would  follow  their  direction,  while  the  overlying 
pitch  kept  on  its  main  course.  So  with  the  glacier :  its  lower  • 
part  within  the  large  valleys  followed  the  directions  of  the 
valleys,  as  the  scratches  and  bowlders  show;  while  the  upper 
portion  had  its  usual  course,  —  the  course  which  is  indicated 
by  the  scratches  elsewhere  over  the  higher  parts  of  the 
country. 

The  cold  of  the  era  may  have  been  mainly  due  to  an  ele- 
vation and  extension  of  Arctic  lands,  increasing  the  area  of 
Arctic  land-ice;  and  to  a  partial  closing,  through  this  eleva- 


216  CENOZOIC  TIME. 


tion,  of  the  Arctic  region  against  the  warm  current  of  the 
Atlantic  Ocean,  the  Gulf  Stream,  which  is  now  a  source  of 
warmth  to  all  of  Northeastern  Europe,  and  even  Iceland, 
Nova  Zembla,  and  the  polar  seas  and  lands.  Other  reasons 
for  cold  have  been  suggested,  references  to  which  will  be 
found  in  large  works  on  the  subject. 

South  America  has  its  Glacial  region,  and  evidences  of 
transportation  toward  the  equator;  so  that  the  phenomena 
described  were  not  confined  to  only  one  hemisphere.  Some 
writers  suppose  it  to  have  been  alternately  in  the  two  hemi- 
spheres. But  the  evidence  of  this  does  not  appear  to  be  satis- 
factory. 

The  moving  glacier  of  New  England  appears  to  have  had 
its  head  in  the  height  of  land  between  the  St.  Lawrence  val- 
ley and  Hudson  Bay;  for  the  scratches  diverge  from  this 
region  over  Eastern  Maine,  New  Hampshire,  Vermont,  and 
New  York,  being  in  "Western  New  York  and  the  region  just 
east  of  Lake  Huron  southwest  in  direction. 

South  of  drift  latitudes  there  were  glaciers  of  great  magni- 
tude about  the  higher  mountains;  and  moraines,  scratches, 
roches  moutonnees,  occur  on  a  grand  scale  in  many  valleys  of 
the  higher  ridges  of  the  Eocky  Mountains  and  the  Sierra 
Nevada,  as  mementos  of  their  former  Glacial  history.  The 
accompanying  sketch  (Fig.  236)  of  roches  moutonnees  in  one 
of  the  higher  valleys  of  Colorado  is  repeated  here  from  page 
61,  because  the  events  indicated  belong  to  the  Glacial  period. 


QUATERNARY  AGE.  — GLACIAL  PERIOD. 


217 


The  roches  moutonnees  extend  along  the  valley  through  an 
ascent  of  nearly  2,000  feet.  At  present  there  are  no  glaciers 
within  500  miles  of  the  place. 


Flar  230. 


View  on  Roche-Moutonnee  Creek,  Colorado. 


In  the  same  era  a  glacier  in  the  Alps  buried  all  Switzer- 
land 2,000  to  4,000  feet  deep  in  ice,  and  left  immense  blocks  > 
of  Alpine  rocks  on  the  Jura  Mountains. 

Depositions  of  earth  and  stones  from  the  glacier  must  have 

been  going  on  to  some  extent  through  the  whole  Glacial  era. 

The  perpetual  grinding  of  stones  against  stones  in  a  glacier  makes 

a  very  fine  clayey  earth ;  and  a  clay  of  this  kind  was  dropped 

10 


218  CENOZOIC  TIME. 


over  the  hills  and  in  the  valleys,  making  thick  deposits;  and 
as  these  deposits  often  contain  large  bowlders,  derived  likewise 
from  the  glacier,  they  are  called  bowlder-days. 

2.  Champlain  Period. 

1.  Melting  of  the  Glacier  and  Deposition  of  the  Drift.  —  The 

larger  part  of  the  deposition  of  the  drift  was  delayed  until 
the  glacier  melted.  There  is  reason  to  believe  that  during 
the  Glacial  period  the  land  over  the  northern  latitudes  stood 
at  a  higher  level  than  now,  and  that  this  was  one  cause  of 
the  occurrence  of  a  cold  era.  Whether  this  were  so  or  not, 
the  glacier  was  made  finally  to  disappear  through  a  sinking 
of  the  land  over  northern  latitudes,  which  brought  on  a 
milder  climate  and  determined,  and  then  hastened,  the  melt- 
ing. This  subsidence  marks  off  the  commencement  of  the 
Champlain  period,  the  second  period  of  the  Quaternary.  The 
earlier  part  of  it  was  the  era  of  the  melting  of  the  great 
glacier.  The  melting  would  have  gone  on  for  a  long  time 
with  extreme  slowness ;  but  when  the  glacier  was  thinned 
down  to  the  last  500  to  1,000  feet,  in  which  part  of  it  the 
most  of  the  gravel  and  stones  were,  it  went  forward  rapidly; 
and  then  took  place  the  pell-mell  dumping  of  gravel  and  stones 
over  the  hills  and  valleys,  with  the  stratification  of  whatever 
fell  into  the  waters.  At  last,  as  the  facts  prove,  there  was  an 
immense  flood  owing  to  the  rapidity  of  the  final  melting;  for 
the  later  depositions  in  many  regions  are  greatly  coarser  than 


QUATERNARY  AGE.  —  CHAMPLAIN  PERIOD.         219 

the  earlier,  the  finer  material  having  been  swept  away  down 
stream  and  into  the  ocean. 

The  Mississippi  valley  was  the  outlet  for  the  waters  of  the 
great  region  it  now  drains;  and  the  flood  during  the  whole 
Glacial  period  must  have  been  great,  and  floating  ice  laden 
with  northern  stones  must  have  often  hurried  off  down  stream 
to  the  Gulf.  But  at  the  final  flood  it  made  thick  deposits 
on  the  way  to  the  Gulf,  as  observed  by  Hilgard,  and  in 
Mississippi  bowlders  as  large  as  a  bushel  basket  are  found  in 
the  beds. 

Icebergs  thus  despatched  to  the  Mexican  Gulf  must  have 
made  havoc  of  the  warm- water  life;  and  it  is  therefore  no 
occasion  for  surprise,  as  Hilgard  remarks,  that  the  sea-shore 
drift  deposits  contain  no  marine  species  of  shells. 

The  subsidence,  with  which  the  Champlain  period  opened, 
was  greatest  to  the  north,  being  over  500  feet  on  the  St. 
Lawrence  near  Montreal,  400  feet  on  Lake  Champlain,  over 
200  feet  on  the  shores  of  Maine,  and  but  40  to  100  feet  along 
Southern  New  England.  The  river-beds  hence  did  not  have 
even  their  present  slope,  and  consequently  the  rivers  in  part  be- 
came great  lakes.  For  the  same  reason  the  flood  waters  made 
deposits  of  great  breadth  along  the  river  valleys  and  lake  re- 
gions,—  the  greatest  fresh- water  deposits  of  geological  history. 
The  depth  of  the  submergence  at  Montreal,  on  Lake  Cham- 
plain,  along  the  coast  of  Maine,  and  most  other  points  on 
the  sea-coast  is  proved  by  the  occurrence  of  sea-shore  depos- 


220  CENOZOIC  TIME. 


its  full  of  sea-shells  at  the  heights  just  stated.  In  the  beds 
on  Lake  Champlain  the  bones  of  a  whale  have  been  exhumed, 
which  lived  in  the  waters  of  the  lake  in  the  Champlain  pe- 
riod, when  it  was  a  great  arm  of  the  enlarged  St.-  Lawrence 
Gulf.  All  the  rivers  and  lakes  over  the  continent  in  the  lati- 
tudes north  of  40°,  and  partly  those  south  of  it,  have  high 
alluvial  plains  at  a  level  far  above  the  river  or  lake  they 
border;  and  they  were  made  in  this  Champlain  period  when 
the  land  was  below  its  present  level. 

2.  Champlain  Period  after  the  melting.  —  After  the  melting 
was  completed,  the  rivers,  though  still  at  flood  height,  were 
more  quiet  in  their  action,  and  they  made  depositions  in 
the  river- valleys,  wherever  these  were  not  already  filled  to 
the  flood  level,  of  a  finer  alluvium;  and  much  of  this  allu- 
vium contains  fresh-water  shells,  and  occasional  bones  of 
quadrupeds.  The  amount  of  sand,  gravel,  and  clay  which 
had  been  dropped  over  the  hills  by  the  ice  was  immense, 
and  it  lay  loose,  easy  to  be  taken  up  by  streams  the  rains 
might  make;  and  hence  the  filling  of  the  valleys  even  after 
the  ice  had  disappeared  may  have  gone  forward  for  a  while 
with  much  rapidity.  But  the  finer  alluvium  shows  that 
before  the  Champlain  period  ended  the  flow  of  the  larger 
streams  was  comparatively  quiet. 

In  Europe  and  Great  Britain  the  Champlain  period  was  one 
of  subsidence  over  the  higher  latitudes,  as  in  America,  and 
the  subsidence  was  greatest  to  the  north.  In  Prance  and 


QUATERNARY  AGE.  — RECENT  PERIOD.  221 

Belgium   the   depression   below   the   present   level   was    50    to  j     (__ 
100  feet;  in  Southern  England,  100  to  200  feet;  in  Northern 
England  and  Scotland,  as  reported  by  British  geologists,  1,000  ( 
to  1,400  feet.     In  Sweden  it  was  200  at  the  south  to  400  or  </ 


500  to  the  northeast,  —  so  great  that  an  ocean  channel  then 
connected  the  Baltic  with  the  White  Sea.  The  alluvial  deposits 
on  the  Rhine,  below  Basle,  are  in  some  places  800  feet  or  J 
more  in  height  above  the  river.  But  this  height  does  not 
indicate  a  depression  of  as  great  an  amount  in  the  Cham- 
plain  period;  for  much  of  it  was  owing  to  the  piling  of  the 
flooded  waters  in  the  narrow  valley.  The  distance  from  Basle 
in  a  straight  line  to  the  North  Sea  at  the  mouth  of  the  Rhine 
is  about  400  miles;  and  if  the  flood  from  the  melting  glacier 
increased  the  slope  of  the  surface  of  the  waters  on  an  average 
only  2  feet  a  mile,  the  flood  level  at  Basle  would  have  been 
800  feet  above  the  present  level  of  the  river. 

3.    Recent  Period. 

The  Champlain  period  was  brought  to  a  close  by  a  raising 
of  the  land  over  the  higher  latitudes,  bringing  the  continent 
finally  up  to  its  present  level.  This  elevation  placed  the  old 
sea-beaches  of  the  Champlain  period  high  above  the  sea,  at 
their  present  level,  that  is,  over  500  feet  near  Montreal,  over 
200  feet  on  the  coast  of  Maine,  and  so  on,  as  above  stated; 
and  this  level  is  approximately  a  measure  of  the  elevation. 
River- valleys,  after  the  rise,  had  a  much  steeper  slope  than  in 


222 


CENOZOIC  TIME. 


the  Champlain  period,  and  hence  their  flow  was  increased  in 
rate.  They  consequently  went  on  cutting  down  their  beds 
through  the  Champlain  deposits  of  the  valley  to  a  lower  level; 
and  at  the  time  of  their  annual  floods  they  wore  away  the 
deposits  on  either  side  of  the  channel,  making  thereby  an 
alluvial  flat  or  flood-ground,  —  for  every  river  has  a  flood- 
ground  which  it  covers  in  its  times  of  flood,  as  well  as  a 
channel  for  dry  times.  This  sinking  of  the  river-beds  left 
the  old  flood-grounds  as  a  high  terrace  far  above  the  level  of 

Fig.  237. 


Terraces  on  the  Connecticut  River,  south  of  Hanover,  N.  H. 

the  stream;  and  the  great  elevated  plains  still  remain  to  at- 
test to  the  vastness  of  the  floods  from  the  melting  glacier. 
In  the  course  of  the  elevation  a  series  of  terraces  was  often 


QUATERNARY  AGE.  — RECENT  PERIOD.  223 

made  along  the  valleys,  as  illustrated  in  the  accompanying 
view  (Fig.  237).  A  section  of  a  valley  thus  terraced  is  repre- 
sented in  Pig.  238.  The  formation  terraced  is,  as  is  shown, 
the  Champlain;  and  in  the  Champlain  period  it  filled  in  gen- 
eral the  valley  across  (from  f  to  f),  excepting  a  narrow 
channel  for  the  stream,  the  whole  breadth  having  been  the 

Fig.  238. 


Section  of  a  valley  with  its  terraces  completed. 

flood-ground  of  the  Champlain  River.  But  after  the  elevation 
of  the  land  that  closed  the  Champlain  period  began,  the  river 
commenced  to  cut  down  through  the  formation,  making  one 
or  more  terraces  in  it,  on  either  side  of  the  stream.  In  Fig. 
238,  R  is  the  position  of  the  river-channel  after  the  terra- 
cing; and  on  either  side  of  it  there  are  terraces  at  the  levels 
ff't  d  d',  b  b',  and  also  another  on  the  right  side  at  r. 
These  terrace-plains  are  usually  the  sites  of  villages.  They  add 
greatly  to  the  beauty  of  the  scenery  along  all  water-courses. 
The  terraces  fail  where  the  valley  is  narrow  and  rocky. 

Between  the  Champlain  and  Recent  periods,  or  in  the  open- 
ing part  of  the  latter,  Europe  passed  through  a  second,  but 
less  severe  Glacial  epoch.  Marks  of  it  have  been  pointed 
out  in  glacial  deposits  in  the  Alps  and  other  places,  but  espe- 


224  CENOZOIC  TIME. 


cially  through  the  occurrence  in  great  quantities  of  remains 
of  the  Reindeer,  a  high-latitude  animal,  in  Southern  France. 
With  the  bones  of  the  Reindeer  there  are  also  those  of 
other  cold-climate  species.  This  epoch  is  called  the  Rein- 
deer era;  and  the  part  of  the  Eecent  period  following  it 
the  Modern  era. 

4.    Life  of  the  Quaternary. 

L  General  Observations,  —  The  plants  and  the  lower  tribes 
of  the  Animal  kingdom  in  the  early  part  of  the  Quaternary 
were  essentially  the  same  as  now.  The  species  of  corals  mak- 
ing coral-reefs  in  the  tropics  were  probably  in  existence  and 
at  work  before  the  close  of  the  Tertiary  age;  and  the  same 
is  true  of  part  of  the  Insects,  Eishes,  Reptiles,  Birds,  and 
Mammals  of  the  modern  world,  perhaps  of  a  large  part. 

There  must  have  been  some  exterminations  as  a  conse- 
quence of  the  cold  of  the  Glacial  period,  and  of  the  ice  of 
high  latitude  regions.  Many  plants  were  driven  south  by 
the  coming  on  of  the  cold,  and  thus  escaped  destruction;  and 
some  of  these  now  live  on  Mount  Washington  and  other  high 
summits  of  temperate  North  America.  Birds  must  have  short- 
ened their  northward  migrations  and  lengthened  them  south- 
ward, and  for  the  most  part  may  have  escaped  catastrophe. 
The  beasts  of  prey,  cattle,  and  other  large  mammals  of  Drift 
latitudes  must  also  to  a  great  extent  have  moved  toward  the 
tropics  as  the  rigors  of  the  approaching  ice-period  began  to 


LIFE  OF  THE  QUATERNARY  AGE.  225 

be  felt.  Certain  it  is,  that  after  the  ice  had  gone  there  was 
a  large  population  of  brute  Mammals  over  Europe  and  the 
other  continents ;  and  facts  seem  to  prove  that  they  hung 
about  the  southern  limit  of  the  ice,  and  often  moved  north- 
ward with  the  lulls  in  the  intensity  of  the  climate  or  thej 
shortening-in  at  intervals  of  the  ice-field. 

2.  Brute  Mammals.  —  The  brute  mammals  reached  their  maxi- 
mum in  numbers  and  size  during  the  warm  Champlain  period, 
and  many  species  lived  then  which  have  since  become  extinct. 
Those  of  Europe  and  Britain  were  largely  warm-climate  spe- 
cies, such  as  now  are  confined  to  warm  temperate  and  tropical 
regions ;  and  only  in  a  warm  period  like  the  Champlain  could 
they  have  there  thrived  and  attained  their  gigantic  size.  The 
great  abundance  of  the  remains  and  their  condition  show  that 
the  climate  and  food  were  all  the  animals  could  have  desired. 
They  were  masters  of  their  own  wanderings  and  had  their 
choice  of  the  best. 

The  relics  have  been  found  in  deposits  along  the  margins 
of  rivers  and  lakes;  in  marshes,  where  they  were  mired;  in 
caves,  buried  in  the  stalagmite  (page  24)  that  had  been 
deposited  over  them.  In  Britain  and  Europe  the  caves  were 
the  haunts  of  Bears,  Hyenas,  and  Lions,  much  larger  than 
any  of  the  kind  now  living ;  these  beasts  of  prey  dragged 
into  them  the  bodies  of  the  animals  they  fed  upon.  The 
Cave-Bear  resembled  much  the  Grizzly  Bear  of  Western 
North  America;  and  the  Cave-Hyena  and  Cave-Lion  are  re-j 
10*  o 


226  CENOZOIC  TIME. 


garded  as  the  same  in  species  with  the  African   Hyena   and 
(   Lion,  although  these  modern  kinds  are  dwarfs  in  comparison. 
With  these  there   were  in  Britain  and  Europe   species  of 
Bhinoceros,  a  Hippopotamus,  the  Siberian  Elephant  or  Mam- 
moth, the  Brown  Bear,  Wolf,  Wildcat,  Lynx,  Leopard,  Fox, 
Elk,  Deer,  and  others.     The  modern  Horse  was  among  them, 
/yet  gigantic  in  size  like  many  of  the  other  Mammals  of  that 
V  genial  period.    The  Irish  Deer  (Cervus  megaceros),  skeletons  of 
which  have  been  found  in  Irish  bogs,  had  a  height  to  the  tip 
/  of  the  antlers  of  10   to   11  feet,  and  the  span  of  the  antlers 
was  sometimes  12  feet.     The  Elephant  (lElephas  primigenius) 
and  the  most  common  Ehinoceros  (B.  tichorinus)  had  a  hairy 
covering,  and  this  fitted  them  to  wander  off  into  regions  far 
north;   their   remains,  especially  those  of  the   Elephant,  show 
that  they  lived  in   great  herds   over  Northern  Siberia,  where 
now  the  mean  temperature  of  the  year  is  5°  to  10°  F.     The 
Ehinoceros  had  a  length  of   114  feet,  and  the  Elephant  was 
nearly  a  third  taller  than  the  largest  of  modern  Elephants. 

In  North  America  also  there  were  large  Lions  and  Bears, 
but  none  of  them,  as  far  as  known,  made  caves  their  dens. 
The  largest  of  the  species  was  the  Mastodon  (Fig.  239),  an 
animal  with  tusks  and  trunk  like  an  Elephant.  When  full 
grown  it  was  12  to  13  feet  in  height,  and  to  the  extremities 
of  the  tusks  25  feet  long.  The  teeth  had  a  crown  as  large  in 
area  as  this  page,  and  of  the  form  shown  in  Fig.  240.  Skele- 
tons have  been  found  in  marshes  where  the  heavy  beasts  were 


LITE  OF  THE  QUATERNARY  AGE. 


227 


mired;  and  portions  of  their  undigested  food  —  the  small 
branches  of  spruces  and  other  trees  —  have  been  taken  from 
between  their  ribs,  where  the  stomach  once  was. 


Fig.  239. 


Skeleton  of  Mastodon  Americanos. 

There  were  also  American  Elephants  of  great  size,  much 
resembling  the  Siberian.  Fig.  241  represents  a  tooth  of  one 
of  them  found  in  Ohio ;  it  is  a  little  larger  than  that  of  the 
Mastodon.  There  were  also  Horses  of  large  size,  Tapirs,  Oxen, 
Beavers,  and  various  gigantic  species  of  the  tribe  of  Sloths. 

The  Sloth  tribe  was  especially  characteristic  of  South 
America.  The  modern  Sloth  is  as  large  as  a  Dog  of  medium. 


228 


CENOZOIC  TIME. 


size.     These  species  of  the  Champlain  period  included  a  Me- 
gatherium  (Fig.  242),  which  was  larger  than  the    largest    of 

Figs.  240,  241. 


.       Teeth  of  Mastodon  and  Elephant. 
Fig.  240,  Mastodon  Americanus  (X  #) ;  241,  Elephas  Americanus  (X  #)• 

existing  Ehinoceroses.     As  the  figure   shows,   it  was  a  lazy 
beast,  —  the  bones  of  the  hind  legs  being  much  like  logs,  and 


Fig.  242. 


Megatherium  Cuvieri  (X  'As). 

those  of  the  fore-feet  furnished  with  hands  a  yard  long  for 


LIFE  OF  THE  QUATERNARY  AGE.  229 

pulling  down  trees  after  raising  itself  erect  on  its  hind 
legs  and  enormous  tail  —  a  third  support  —  for  the  purpose. 
This  is  one  of  many  kinds  of  gigantic  Sloth-like  animals  that 
lived  in  South  America  during  the  era.  Other  related  species 
had  a  shell  somewhat  like  the  modern  Armadillo;  and  these 
also  were  gigantic,  one  of  them  (Fig.  243)  measuring  5  feet 
across  its  shell,  and  having  a  length  of  at  least  9  feet. 

Fig.  243. 


Glyptodon  clavipes  (X  */}0). 


In  Australia  the  Mammals  are  now,  with  some  small  ex- 
ceptions, Marsupials,  the  Kangaroo  being  one  of  them. 
They  were  also  Marsupials  then;  but  the  ancient  kinds  par- 
took of  the  peculiar  feature  of  the  era,  —  great  magnitude, 
some  of  the  species  being  as  large  as  a  Hippopotamus,  one 
having  a  skull  a  yard  long,  and  many  of  them  being  far 
larger  than  any  modern  Marsupial. 

Thus  the  brute  races  of  the  Middle  Quaternary  on  all  the 
continents  exceeded  the  moderns  greatly  in  magnitude.  Why, 
no  one  has  explained. 


230  CENOZOIC  TIME. 


The  genial  climate  of  the  Champlain  period  was  abruptly 
J.  L  terminated.  Eor  carcasses  of  the  Siberian  Elephants  were 
frozen  so  suddenly  and  so  completely  at  the  change,  that  the 
flesh  has  remained  untainted.  Near  the  close  of  the  last  cen- 
tury, one  huge  carcass  dropped  out  of  the  ice-cliff  at  the 
mouth  of  the  Lena,  and  for  a  while  made  food  for  dogs. 
The  existence  of  a  hairy  covering  was  then  first  ascertained. 
A  hairy  Rhinoceros  has  also  been  found  in  the  ice.  This 
change  of  climate  was  probably  connected  with  the  commen- 
cing of  the  Eeindecr  or  second  Glacial  era;  and  it  was  then 
that  the  Reindeer  and  some  other  species  succeeded  in  mi- 
grating to  Southern  France,  there  to  live  until  the  cold  epoch 
had  passed.  The  remains  of  the  Reindeer  are  found  along 
with  those  of  the  Cave-Bear,  Cave-Hyena,  Rhinoceros,  Ele- 
phant, and  other  Champlain  species,  showing  that  all  lived 
together  there  at  that  time. 

3.  Man.  —  Man  was  in  existence  during  the  Champlain 
period;  and  probably  in  its  earlier  part  before  the  ice  had 
disappeared  (a  part  often  included  in  the  Glacial  era  by  geol- 
ogists) . 

Relics,  indicating  that  he  was  a  contemporary  of  the  gigantic 
Champlain  Mammals,  occur  in  various  caverns  and  in  river 
and  lacustrine  deposits,  in  Britain,  Europe,  Syria,  and  in 
other  regions. 

The  relics  of  Man  are  stone  implements,  such  as  arrow- 
heads, hatchets,  pestles,  and  stone  chips  made  in  the  manufac- 


MAN.  231 


ture  of  the  implements ;  bones,  shells,  and  other  materials  hav- 
ing upon  them  his  markings  or  carvings;  his  pottery;  the 
charcoal  left  from  his  fires;  the  bones  of  animals  broken 
lengthwise  to  get  out  the  marrow;  his  own  bones,  skulls  and 
skeletons. 

In  Europe  and  Western  Asia  the  stone  implements  of  the 
earlier  part  of  what  is  sometimes  called  the  Stone  age  are  of 
rude  make  and  unpolished.  This  part  of  the  age  has  been 
called  the  Paleolithic  era  in  human  history,  or  that  of  the  \ 
oldest  stone  implements,  —  the  word,  from  the  Greek,  signi- 
fying old  and  stone.  The  stone  implements  occur  along  with 
bones  of  the  Cave-Bear,  Cave-Hyena,  Mammoth,  Rhinoceros, 
and  several  other  Champlain  species,  and  also  with  the  bones 
of  Man;  and  these  human  relics  are  so  associated  with  those 
of  extinct  Mammals  that  there  is  no  reason  to  doubt  that 
they  were  contemporaries. 

Next  came  the  Reindeer  era.  Its  stone-implements  are  un- 
polished, but  better  made  than  those  of  the  preceding  era. 
Besides  these  there  are  examples  of  bones,  shells,  horn  and 
stone  engraved  with  the  forms  of  animals,  and  others  that  are 
variously  carved,  or  made  into  spear-heads  and  other  forms, 
and  also  perfect  human  skeletons.  Fig.  244  represents  a 
drawing,  on  ivory,  of  the  hairy  Elephant;  it  was  found  in 
the  cave  of  La  Madelaine,  in  Perigord,  Southern  France,  and 
shows  that  the  Elephant  was  well  known  to  the  men  of  the 
period.  These  human  relics  are  associated  with  remains  of 


232 


CENOZOIC  TIME. 


7 


the  same  Champlain  Mammals  that  occur  in  the  earlier  de- 
posits,, and  also  with  great  numbers  of  the  bones  of  the 
Itaindeer,  and  many  of  the  Aurochs,  Elk,  Deer,  and  other 
species  of  later  time. 

Fig.  244. 


Elephas  primigenius ;  engraved  on  ivory  (X  Ys). 

Next  followed  an  era  in  which  the  implements  were  still 
of  stone,  but  often  polished,  and  in  which  the  remains  of  the 
E^indeer  are  rarely  found,  and  those  of  the  peculiar  Cham- 
plain  species  not  at  all,  but  instead  portions  of  skeletons  of 
the  domestic  dog  and  other  existing  quadrupeds,  with  much 
broken  pottery.  This  era  in  the  Stone  age  is  called  the  Neo- 
lithic, from  the  Greek  for  new  and  stone.  The  shell-heaps 
(Kitchenmiddens)  of  the  Danish  Isles  in  the  Baltic  are  among 
the  Neolithic  localities. 

The  bones  and  skeletons  of  Man  of  this  Stone  age  in  no 
case  indicate  a  race  inferior  to  the  lowest  of  existing  races, 
or  intermediate  between  Man  and  the  Man- Apes,  —  the  species 
among  the  brutes  which  approach  him  most  nearly.  But  still 


MAN.  233 

they  are  those  of  uncivilized  Man,  and  in  part  of  Man  of  a 
low  order  of  faculties. 

The  skeleton  of  Neanderthal  (a  part  of  the  valley  of  the 
Diissel,  near  Diisseldorf)  is  the  worst,  but  it  is  not  older 
than  others  having  better  skulls  and  higher  foreheads.  The 
capacity  of  the  cranium  was  75  cubic  inches,  which  is  greater 
than  in  some  existing  men.  A  jaw-bone  of  low  type,  found 
in  the  oldest  Belgian  deposits,  had  little  height  and  great 
thickness,  as  if  for  powerful  use,  and  the  posterior  of  the 
molar  teeth  was  the  largest,  —  a  brutal  feature. 

The  skeletons  of  the  Reindeer  era  in  Southern  Prance  are  in 
part  those  of  men  of  unusual  height,  —  5  feet  9  inches  to 
over  6  feet ;  and  the  skulls  are  large  and  well  shaped,  with 
the  foreheads  high  and  capacious.  They  are  of  better  size  and 
shape  than  many  of  the  Reindeer  era  in  Belgium,  which  are 
small  and  after  the  Laplander  type. 

One  of  the  most  perfect  was  found  in  the  stalagmite  that 
formed  the  floor  of  the  cave  of  Mentone,  near  the  borders  of 
France  and  Italy,  on  the  Mediterranean.  Eight  feet  above  it  in 
the  stalagmite  there  were  remains  of  the  extinct  Rhinoceros 
and  other  Champlain  species.  The  man  would  compare  well, 
if  we  may  judge  from  the  skeleton,  with  the  best  among 
civilized  races,  —  his  forehead  broad  and  high,  and  rising  with 
a  facial  angle  of  85°,  his  height  6  feet;  and  yet  he  was  a 
European  savage  of  the  Reindeer,  if  not  Paleolithic  era;  for 
about  him  lay  his  flint  implements  and  weapons,  his  chaplet 


234  CENOZOIC  TIME. 


of  stag's  canines,  and  shells  that  he  had  gathered  for  food 
or  ornament  from  the  shores  near  by.  The  tibia  or  shin-bone 
was  somewhat  flattened,  a  peculiarity  often  observed  in  the 
skeleton  of  the  American  Indian.  The  brain-cavity  of  a  skull 
found  in  the  cave  of  Cro-Magnon,  in  Southern  Prance,  had  a 
capacity  of  97  cubic  inches,  which  is  very  much  above  that 
of  ordinary  Man,  and  nearly  three  times  that  of  the  highest 
Man-Ape. 

In  North  America  cases  of  the  occurrence  of  ancient  human 
bones  or  skeletons  in  Quaternary  deposits  are  not  as  well 
authenticated  as  those  in  Europe.  Admitting  the  facts  that 
have  been  published,  they  do  not  give  Man  greater  antiquity 
than  those  above  mentioned. 

No  case  of  the  presence  of  human  relics  in  deposits  of  the 
Tertiary  age  on  any  continent  is  yet  well  established.  Mr. 
W.  Boyd  Dawkins,  an  excellent  British  geologist  and  original 
observer  in  this  department  of  the  science,  states,  in  his  recent 
work  on  Cave-Hunting  (1874),  that  the  evidence  obtained 
proves  that  "Man  lived  in  Germany  and  Britain  after  the 
maximum  Glacial  cold  had  passed  away,"  and  that  no  human 
remains  te  have  been  discovered  up  to  the  present  time  in 
any  part  of  Europe  which  can  be  referred  to  a  higher  an- 
tiquity than  the  Pleistocene  (Quaternary)  age."  The  human 
relics  thus  far  found  in  Syria  and  Asia  lead  to  no  greater 
antiquity  for  Man.  Migration  into  Europe  along  with  the 
Champlain  Mammals  in  pre-Glacial  time  is  suspected;  but  on 
this  point  there  are  as  yet  no  known  facts. 


GEOLOGICAL  WORK  STILL  GOING  FORWARD.     235 

The  second  Glacial  epoch  in  Europe  and  Asia  (which 
there  is  reason  to  believe  produced  effects  also  in  North 
America)  appears  to  have  finally  brought  to  a  close  the  era 
of  giant  beasts,  leaving  the  world  for  Man. 

The  Age  of  Man  still  continues;  and  now  it  has  as  its  j 
fossils,  not  only  flint  implements  and  human  bones,  but  also  I 
buried  cities,  temples,  statues,  manuscripts. 

The  system  of  life,  long  in  progress,  finally  reached  its 
completion  in  a  being  that  could  search  into  the  earth's  his- 
tory, study  Nature's  laws,  investigate  the  system  of  the  uni- 
verse, judge  of  right  and  wrong  in  himself  and  others  and 
will  the  right;  and  who  has  thus  the  highest  credentials  of 
kinship  with  the  Infinite  Author  of  physical  and  moral  law. 
The  progress  of  chief  interest  hence  is  no  longer  the  develop- 
ment of  animal  races  and  characters,  but  the  exaltation  of 
Man  in  the  direction  of  his  higher  nature. 

5.    Geological  "Work  still  going  Forward. 

Rock-making  has  not  yet  ceased;  for  the  old  agencies  — 
the  waters,  the  winds,  and  life  —  are  still  at  work  with  un- 
impaired energies.  Sand-beds,  pebble-beds,  and  mud-beds  are 
accumulating  along  sea-shores  and  in  shallow  waters,  precisely 
like  those  that  were  hardened  into  ancient  sandstones,  con- 
glomerates, and  shales;  and  limestones  are  forming  from  shells 
and  corals  similar  to  ancient  limestones.  Moreover,  modern 


236 


CENOZOIC  TIME. 


Fig.  245. 


Dodo,  with  the  Solitaire  in  the  background. 
From  a  painting,  at  Vienna,  made  by  Roland  Savery,  in  1628. 


LENGTH  OE  GEOLOGICAL  TIME.  237 


fossils  include,  besides  human  remains,  corals,  shells,  and 
relics  of  all  the  various  tribes  of  the  era,  as  in  past  time. 

Further,  species  are  becoming  extinct;  at  least  through 
Man,  if  not  in  other  ways.  The  Dodo,  an  extinct  chicken- 
like  bird  of  50  pounds  weight  (Fig.  245),  was  living  on 
Mauritius  in  the  17th  century.  The  Moa,  larger  than  an 
Ostrich,  and  other  birds  with  it,  have  recently  disappeared 
from  New  Zealand.  The  Aurochs  (Bison  prisons]  of  Europe 
is  nearly  extinct.  Thus  wild  animals  have  begun  to  disap- 
pear before  advancing  Man.  The  same  is  true  of  plants. 

Again,  changes  of  level  are  still  going  on.  A  large  part 
of  Sweden  is  rising  at  the  slow  rate  of  4  feet  or  so  a  cen- 
tury, and  as  slowly  a  portion  of  Greenland  is  subsiding. 
Such  movements,  along  with  earthquakes,  prove  that  contrac- 
tion from  the  cooling  of  the  earth's  crust  has  not  ceased. 

Hence,  although  the  earth  is  in  its  finished  state,  enough 
of  geological  work  is  now  going  on  to  enable  Man  to  decipher 
the  records  of  the  past. 


V.  — Observations  on  Geological  History. 

I.    Length  of  Geological  Time. 

To  the  question,  "What  is  the  length  of  geological  time, 
geology  gives  no  definite  reply.  It  establishes  only  the  gen- 
eral proposition  that  time  is  long. 


238  GEOLOGICAL  HISTORY. 

The  Canon  of  the  Colorado  (page  78)  is  a  gorge  200 
miles  long,  bounded  the  most  of  the  way  by  steep  walls 
of  rock  over  3,000  feet  in  height,  cut  through  sandstones, 
limestones,  and  other  rocks,  and  at  bottom  over  parts  of  it, 
for  several  hundred  feet,  into  granite;  and  above  the  lofty 
walls  a  few  miles  back  from  the  stream  the  pile  of  nearly 
horizontal  strata  is  continued  in  mountains  to  a  height  of 

(7,000  to  8,500  feet  above  the  bed  of  the  river.  All  the 
facts,  as  its  describers  testify,  point  to  running  water  as  the 
agent  that  made  the  great  channel.  The  region  was  under 
the  sea  until  the  close  of  the  Cretaceous  period,  for  marine 
Cretaceous  strata  are  the  uppermost  rocks.  It  follows,  then, 
that  all  this  extensive  excavation  was  accomplished  by  slow- 
acting  water  during  Cenozoic  time.  Surely  Cenozoic  time  was 
very  long. 

The  gorge  of  the  Niagara  Eiver  below  the  Falls  has  a 
length  of  7  miles.  It  is  the  work  of  the  waters  since  the 
middle  of  the  Champlain  period;  for  in  the  first  place,  a 
former  channel  leading  from  the  Whirlpool  toward  Lake  On- 
tario was  entirely  filled  by  the  gravel  and  sands  thrown  in 
by  the  melting  glacier  during  the  earlier  part  of  that  period; 
.  and,  secondly,  Champlain  beds  containing  shells  of  Lake  Erie 
and  a  tooth  of  the  Mastodon,  formerly  spread  over  the  place 
where  the  gorge  now  is,  as  shown  by  the  remains  of  the  for- 
mation above  on  the  Canada  side.  The  water  has  conse- 
quently made  this  vast  excavation,  7  miles  long,  since  Man 


LENGTH  OF  GEOLOGICAL  TIME.  239 

appeared.      The   rate   of  progress   of  the  Falls  up  stream  is 
not   satisfactorily   ascertained;    the    most  rapid  rate  that  has 
been  estimated  would  give  more  than   30,000  years  for  they 
work. 

The  thickness  of  a  sedimentary  deposit  is  no  satisfactory 
basis  for  determining  the  length  of  time  it  took  to  form.  In 
a  sea  100  feet  deep  100  feet  of  sediment  may  accumulate; 
and  the  thickness  could  not  exceed  this  (except  a  little  through 
wave-action  and  the  winds)  if  a  million  of  years  were  given 
to  it. 

Let  the  same  region  be  undergoing  a  subsidence  of  an  inch 
a  century,  and  the  thickness  might  increase  at  that  rate;  and 
much  faster  if  a  yard  a  century;  and  with  either  rate,  giving 
time  enough,  any  thickness  might  be  attained.  Hence  a  stra- 
tum of  sandstone  100  feet  thick  may  have  been  formed  in  a 
thousandth  part  of  the  time  of  a  thin  intervening  bed  of  shale. 

Nevertheless,  the  aggregate  maximum  thickness  which  the 
strata  attained  during  the  several  ages  may  be  used  for  an 
approximate  estimate  of  the  comparative  lengths  of  those 
ages.  On  such  data,  it  is  ^deduced  that  the  time-ratio  for 
Paleozoic,  Mesozoic,  and  Cenozoic  time  was  not  far  from 
12  :  3  :  1.  Consequently,  if  we  suppose  the  length  of  time 
since  the  Paleozoic  began  to  be  16  millions  of  years,  Paleo- 
zoic time  will  include  12  millions,  Mesozoic  3  millions,  and 
Cenozoic  1  million.  Most  geologists  would  make  the  whole 
interval  several  times  16  millions. 


240  GEOLOGICAL  HISTORY. 


2.   Progress  in   Features. 

The  earth  through  the  ages  made  progress, — 

1.  In  its  surface  features:   from  the  condition  of  a  melted 
sphere  as  featureless  as  a  germ,,  to  that  of  an  almost  univer- 
sal ocean  with  small  lands,  —  enough  of  land  to  mark   out 
the  feature-lines  of  the  future  continents;  and  at  last  —  after 
slow   expansion   southward,    a   lifting   of  mountain   ranges  at 
long  intervals,  and  a  retreating  of  the  waters  —  to  the  exist- 
ence of  great  continents   having  high  mountain  borders  and 
well- watered  interior  plains. 

2.  In  its  river-systems:    from  the   existence  of   only   little 
streamlets   draining   small  lands  in  the  Archaean  and  Silurian 
eras,  and  making  no    permanent  geological  record  beyond   a 
rain-drop  impression;  to  a  condition  of  vast  fresh-water  lakes 
and  marshes  when  beds  of  vegetable  material  accumulated  for 
the  making  of  coal-beds;  and  finally  to  that  of  the  completed 
continent,  when    a    single    river    with    its    tributaries    drains, 
waters,  and  contributes   fertility  to  hundreds  of  thousands  of 
square  miles  of  surface,  and  the  work  of  fresh  waters  in  rock- 
making  exceeds  that  of  the  ocean. 

3.  In  its  climate:   from  a   condition   of  general  uniformity 
of  temperature,  to,  at  last,  —  though  with  interrupted  progress, 
—  that  of  the   present   diversity,  when  the   poles  have  a  per- 
manent  capping  of  ice,  and  only  the   equatorial   regions   per- 
petual verdure. 


PROGRESS  IN  FEATURES.  241 

4.  And,  again,  in  its  living  adornments:  from  an  era  when 
the  ^small  rocky  lands  were  bare,  or  gray  and  drear  with 
lichens,  and  all  other  life  was  of  the  simplest  kind  and  below 
the  water-level;  to  a  time  of  flowerless  forests  and  jungles 
over  immense  plains,  yet  with  no  sounds  from  living  Nature 
more  musical  than  the  Amphibian's  croak;  and  onward  to 
the  better  time  when  the  earth  abounds  in  flowers  and  fruits 
and  birds,  and  is  covered  with  the  homes  of  Man. 

3.   The  System  of  Nature  of  the  Earth   had  a  beginning 
and  will   have  an  end. 

A  system  of  progress  or  development  in  the  earth  as  much 
implies  that  it  had  a  beginning,  as  that  in  any  plant  or  ani- 
mal. Man,  Mammals,  Fishes,  Mollusks,  Rhizopods,  Plants, 
all  had,  according  to  geological  history,  their  beginning;  so 
also  mountains,  valleys,  rivers,  continents,  rocks.  And  so 
also  the  earth;  and  therefore  the  system  of  nature,  whose 
development  went  forward  in  and  through  it,  had  its  begin- 
ning. 

If  this  is  true  of  one  sphere  in  space,  we  may  rightly  take 
another  step  and  assert  that  the  universe  had  its  beginning. 

It  also  admits  of  demonstration  that  the  earth  will  have  its 
end.  A  finished  state  is  always  the  state  before  decline  and 
death.  The  earth  is  dependent  for  all  the  beauty  in  its  liv- 
ing adornments,  and  even  for  the  existence  of  its  life,  on  the 
heat  and  light  of  the  sun.  The  sun  is  losing  annually  its 
11  * 


GEOLOGICAL  HISTORY. 


heat;  and  however  infinitesimal  the  amount  of  loss,  it  is  sure 
to  end  in  a  cooled  and  dark  sun;  and  hence,  even  long  be- 
fore the  sun  is  cold,  the  earth,  supposing  it  to  have  met  with 
no  earlier  catastrophe,  will  have  become  dark  and  lifeless,  — 
literally  a  dead  earth. 

4.    Progress  in  Life. 

1.  The  progress  in  life  was  in  general  from  the   simpler 
forms  to  the  more  complex,  or  from  the  low  to  the  high.  — 

This  truth  has  been  illustrated  in  each  chapter  of  the  pre- 
ceding geological  history. 

2.  The  progress  was  by  gradual  steps.  —  Species  appeared 
and  disappeared,  not  only  at  the  beginning  of  ages,  or  of  the 
subdivisions  of  ages  called  periods,  but  also  during  the  pro- 
gress of  periods,  each  of  the  successive  strata  containing  some 
fossils  not  found  below,  and  failing  of  others  that  are  abun- 
dant in  underlying  beds.     There  were  at  times  epochs  of  wide- 
spread  catastrophe,   ending   periods,   and  two   of  them,   those 
closing   Paleozoic    and    Cenozoic   time,    were   nearly   or   quite 
universal  for  the  continental  seas.     But   these  must   have  left 
unharmed  the  life  of  the  deep  ocean;  and  they  may  not  have 
exterminated  all  the  life  of  the  emerged  land,  or  even  of  the 
whole  area  of  continental  seas. 

3.  The  progress  was  according  to  system.  —  The  first  animal 
life  was  probably  the  Protozoan,  —  or  Ehizopods,  Sponges,  and 
the  like;    kinds  that  are  minute   and  destitute   of  members. 


PROGRESS  IN  LIKE.  248 

But  later  the  four  great  systems  of  structure  —  the  Radiate, 
Mollusk,  Articulate,  and  Vertebrate  —  were  denned;  and  the 
species  which  appeared  afterward  in  the  long  succession  were 
constructed  according  to  one  or  the  other  of  these  systems. 
Each  system,  by  the  new  species  that  came  into  existence  as 
time  moved  on,  became  displayed  in  higher  and  more  diver- 
sified forms.  The  first  of  the  Vertebrates  were  the  Fishes,  — 
the  simplest  of  its  tribes.  Even  in  these  limbless  species 
the  arms  and  legs  of  the  higher  Vertebrates  were  present, 
though  only  in  the  state  of  fins;  and  the  lung,  though  only 
as  a  cellular  air-bladder ;  and  the  ear,  though  only  as  a  closed 
cavity  containing  a  loose  bone;  and  so  with  other  parts. 
Thus  the  earliest  of  Vertebrates  possessed  in  an  incipient  stage 
many  of  the  organs  that  became  fully  developed  in  the  later 
and  higher  Vertebrates.  And  in  the  succession  of  species  that 
existed,  all  were  made  on  the  fish-structure  as  its  basis,  even 
the  species  of  the  highest  class,  —  those  of  Mammals  and 
Man.  A  zoologist,  in  order  to  understand  the  fundamental 
elements  in  the  human  structure,  goes  to  the  fish  and  the 
frog  for  instruction;  and  Nature  is  so  true  to  her  funda- 
mental principles,  that  he  there  finds  what  he  looks  for. 

4.  The  system  of  progress  is  rightly  called  a  system  of  de- 
velopment or  evolution.  —  With  every  step  there  was  an  un- 
folding of  a  plan,  and  not  merely  an  adaptation  to  external 
conditions.  There  was  a  working  forward  according  to  pre- 
established  methods  and  lines  up  to  the  final  species,  Man, 


244  GEOLOGICAL  HISTORY. 

and  according  to  an  order  so  perfect  and  so  harmonious  in 
its  parts,  that  the  progress  is  rightly  pronounced  a  develop- 
ment or  evolution.  Creation  hy  a  divine  method,  that  is,  by 
the  creative  acts  of  a  Being  of  infinite  wisdom,  whether  through 
one  fiat  or  many,  could  be  no  other  than  perfect  in  system, 
and  exact  in  its  relations  to  all  external  conditions,  —  no  other, 
indeed,  than  the  very  system  of  evolution  that  geological  history 
makes  known. 

5.  The  system  not  one  of  regular  progress  upward,  but  one 
involving  the  culmination  and  decline  of  some  tribes  as  the 
general  unfolding  went  forward.  —  As  has  been  brought  out 
in  the  history,  the  division  of  Trilobites,  Brachiopods,  and 
Crinoids,  besides  others,  reached  their  maximum,  or  culminated, 
in  Paleozoic  time;  of  Amphibians,  in  the  first  period  of  the 
Mesozoic  era;  of  Eeptiles  and  Ganoids  among  Vertebrates, 
and  of  Cephalopods,  the  highest  of  Mollusks,  in  the  later 
Mesozoic;  of  brute  Mammals,  in  the  Champlain  period  of 
Cenozoic  time.  So,  again,  in  the  kingdom  of  plants,  the 
highest  Cryptogams  —  the  Acrogens  —  culminated  in  the  Car- 
boniferous period,  that  is,  the  later  Paleozoic;  Cycads,  in  the 
middle  Mesozoic ;  while  Palms  and  Angiosperms  have  the  present 
era  as  their  time  of  greatest  display  and  perfection.  These 
are  a  few  examples,  showing  that  progress  did  not  go  on 
regularly  upward;  but  that  the  old,  not  only  in  species,  but 
also  in  tribes  and  orders,  were  culminating  and  then  passing 
away,  as  new  and  higher  tribes  were  introduced,  in  the  pro- 
gressing evolution  of  the  kingdoms  of  life. 


PROGRESS  IN  LIJFE.  245 

6.  Parallelism  between  the  progress  of  the  system  of  life  and 
the  progress  of  individual  life.  —  An  animal,  in  its  growth  from 
the  germ,  —  or,  as  it  is  called,  its  embryonic  development,  — 
passes  through  a  succession  of  forms  before  reaching  the  adult 
state.  In  Mammals  the  changes  after  birth  are  small,  the  larger 
part  of  them  having  taken  place  before  birth.  But  in  the  lower 
animals  the  successive  forms  are  often  widely  diverse,  and  they 
frequently  mark  successive  stages  in  the  life  of  the  animal. 
Thus,  in  Insects,  there  is  the  caterpillar  or  grub  stage,  before 
the  adult;  and  in  many  Crustaceans,  Mollusks,  Worms,  and 
Radiates  there  are  several  such  stages. 

Now  species  have  existed  —  and  many  now  exist  —  which 
have  the  general  characters  of  the  forms  in  these  lower  stages ; 
and,  in  accordance  with  the  above  proposition,  the  order  of  their 
appearance  in  the  geological  series  is,  in  general,  as  announced 
by  Agassiz,  that  of  their  development  in  the  embryonic  series. 
Thus,  as  the  worm-like  grub  precedes  the  adult  insect,  so 
Worms,  in  geological  history,  preceded  Insects.  As  a  fish-like 
condition  of  an  Amphibian  precedes  the  adult  form  in  which 
the  fish-like  feature  is  lost,  so  Fishes  preceded  Amphibians. 
The  examples  of  the  principle  are  numerous.  Some  authors 
have  so  great  faith  in  it,  that  they  are  ready  to  decide  as  to  the 
form  of  the  earliest  species  of  a  tribe  from  the  earlier  stages 
in  individual  development.  But  this  is  unsafe,  since  such  forms 
may  have  come  late  into  the  system  of  life  as  well  as  early; 
inasmuch  as  progress  was  not'  in  all  cases  upward  progress. 


246  GEOLOGICAL  HISTORY. 

Where  the  parallelism  above  mentioned  is  not  apparent  in 
the  general  form  or  structure,  it  is  still  manifested  in  certain 
comprehensive  laws  common  to  both  kinds  of  progress,  the 
geological  and  embryonic.  The  following  are  some  of  these 
laws. 

a.    The  low  before  the  relatively  high. 

6.  The  simple  before  the  complex.  A  germ  has  little  dis- 
tinction of  parts ;  the  animal  it  is  to  evolve  is  there  in  a  very 
general  condition,  that  is,  without  any  special  organs.  As  de- 
velopment of  a  Mammal  goes  on,  the  denning  of  the  head  be- 
gins, and  this  is  one  of  the  first  steps  in  the  evolving  of  special 
parts,  or  in  the  specialization  of  the  structure.  Protuberances 
also  form  and  commence  the  defining  of  the  limbs ;  and  then, 
finally,  the  parts  of  the  limb  become  distinct,  or  are  specialized. 
Thus  it  is  throughout  the  structure,  until  the  specialization  of 
the  parts  peculiar  to  the  particular  animal  is  completed. 

This  law  of  the  general  before  the  special  is  a  law  also  in 
the  geological  progress  of  the  system  of  life.  In  a  fish,  the 
earliest  of  Vertebrates,  the  vertebrate  structure  is  exhibited  in 
its  most  generalized  condition.  The  vertebral  column  consists 
of  one  single  uniform  range  of  vertebrae  without  a  neck  portion, 
and  without  a  pelvis  to  divide  the  body  from  a  tail  and  afford 
support  to  hind  limbs ;  the  limbs  are  fins,  and  hence  only  rudi- 
ments of  limbs  ;  the  vertebrae  have  great  simplicity  of  form ; 
the  teeth  are  all  of  the  simplest  kind ;  the  lung  is  merely  an 
air-bladder,  and  so  on.  Thus,  all  through  the  structure,  a  fish 


PROGRESS  IN  LIFE.  247 

is  an  exhibition  of  the  vertebrate  type  in  a  generalized  state. 
The  Vertebrates  which  succeeded  to  fishes,  the  Amphibians, 
have  the  grand  divisions  of  the  body  well  brought  out,  and  are 
specialized  also  as  to  limbs  even  to  the  toes,  and  in  other  ways. 
Passing  onward  in  time,  the  new  Vertebrates  appearing  exhib- 
ited successively  a  more  and  more  complete  specialization  of 
organs  and  functions,  up  to  Man.  In  the  development  of  Man 
from  the  embryo,  it  is  not  true  that  he  passes  through  a  fish- 
like  condition ;  but  it  is  the  case  that  certain  fish-like  charac- 
teristics may  be  observed  in  the  structure,  during  its  earlier 
progress  ;  and  one  of  these  is  an  opening  beneath  the  jaws,  ( 
which  Dr.  Wyman  has  regarded  as  representative  of  the  gill-  j 
openings  of  Fishes. 

This  law  of  progress  by  specialization  has  its  exceptions ;  for 
Snakes,  which  are  limbless,  succeeded  to  higher  reptiles  which 
had  limbs.  But  such  cases  only  exemplify  another  fact,  al- 
ready illustrated,  —  that,  while  upward  progress  was  the  rule, 
there  was  also  progress  downward,  and  especially  after  the  time  S  v 
of  culmination  of  a  tribe  had  passed. 

c.  Stationary  forms  sometimes  before  the  locomotive.  Thus, 
(1.)  Crinoids,  part  of  the  earliest  life  of  the  globe,  were  sta- 
tionary species  living  attached  by  a  stem;  and,  after  these, 
there  were  free  Asterioids.  So  the  young  of  the  modern  Cri- 
noid  has  a  stem  for  attachment,  and  loses  it,  in  many  spe- 
cies, as  it  becomes  an  adult  (a  Comatulid).  (2.)  The  earliest 
Brachiopods  were  attached  species,  and  so  are  the  young  of 
all  existing  Brachiopods. 


248  GEOLOGICAL  HISTORY. 

d.  Forms  in  a  group  having  the  body  elongated  posteriorly, 
and  endowed  behind  with  locomotive  power,  generally  precede 
those  that  are  shorter  behind  and  superior  in  the  anterior  por- 
tion of  the  body  and  head,  —  a  headward  transfer  of  the  forces 
of  the  structure  marking  all  upward  progress.  The  young  of  a 
crab  has  an  elongated  locomotive  tail-extremity,  which  it  loses 
as  it  develops  to  a  crab  ;  and  so  the  long-tailed  shrimps  pre- 
ceded crabs  in  geological  history.  The  young  of  a  modern 
Ganoid  or  gar-pike  has  an  elongated  verteb  rated  tail,  which  it 
loses  with  the  change  to  the  adult;  and  so  Ganoids  in  Palae- 
ozoic time  had  vertebrated  tails,  but  in  Mesozoic  time  lost  them. 
In  the  young  of  some  birds  the  tail  segments  of  the  vertebral 
column  are  much  elongated  and  free,  but,  with  progressing 
development,  they  become  greatly  contracted,  and  often  con- 
solidated together;  and  so  the  earliest  Birds,  in  part,  at  least, 
had  long  vertebrated  tails.  The  young  of  an  Insect  is  an  elon- 
gated, worm-like  grub ;  and  so  Worms  preceded  Insects.  The 
embryo  of  Man  in  an  early  stage  of  development  has  a  tail  half 
as  long  as  that  of  a  dog  in  the  same  stage. 

The  principle  is  a  general  one  through  the  animal  king- 
dom. This  shortening  behind  is  directly  connected  with,  or 
a  consequence  of,  a  transfer  forward  of  the  forces  of  the  ani- 
mal structure  by  which  improvement  is  given  to  the  anterior 
extremity,  and  a  higher  grade  of  power  and  functions  to  the 
head.  Progress  from  the  embryo  in  animals  is  always  attend- 
ed with  a  gradual  improvement  of  the  head  extremity,  and 


PROGRESS  IN  LIEE.  249 

also  with  changes  of  form   in   adaptation   to  it ;  and,  parallel 
with   this,  progress    in   the    system    of   animal    life,   from   its 
earliest   beginnings  onward,  was   similarly  attended,  under   all 
tribes,  by  a  headward  transfer  of  power  in  the  being,  and  by 
such   structural  changes  as   this   involved.     Marsh  has  shown 
that  the  Carnivores  and  Herbivores  of  the  early  Tertiary  had  ( 
brains  but  a  half  or  a  third  as  large  in  bulk  as  those  near-  ( 
est  related  to  them  in  type  and  size  among  modern  species. 

This  kind  of  progress  is  progress  in  capitalization ;  this 
term  being  derived  from  the  Greek  for  head.  And  the  prin- 
ciple here  illustrated  may  be  briefly  announced  as  follows : 
Progress  both  in  the  system  of  animal  life  and  in  individual 
life  is  eminently  progress  in  cepJialization. 

Man,  the  last  and  highest  being  in  the  system  of  life,  de- 
rives his  exalted  position  from  the  extreme  degree  of  cephaliza- 
tion  which  characterizes  his  structure.  Besides  having  a  great 
brain  and  great  head  power,  his  fore-limbs  are  removed  from 
the  locomotive  series,  and  turned  over  to  the  service  of  the 
head,  and,  as  is  involved  in  this  transfer,  his  body  is  erect. 
Thus,  by  an  abrupt  transition,  he  stands  apart  from  the  ape 
and  all  brute  races. 

7.  The  transitions  between  species,  in  the  system  of  progress, 
not  yet  proved  to  be  gradual  —  The  systematic  succession  in 
the  progress  of  life,  made  manifest  by  facts  derived  from  the 
rocks,  leads  many  to  hold  that  the  whole  has  been  as  much  a 
growth  under  the  control  of  physical  law  as  is  proved  to  be 


250  GEOLOGICAL  HISTORY. 

true  of  the  development  of  the  earth's  features.  Geological 
history  has  accordingly  been  appealed  to  for  evidence  as  to 
whether  species,  instead  of  being  independent  types  of  structure, 
are  so  linked  together  by  gradual  transitions,  that  we  cannot 
reasonably  avoid  the  conclusion  of  their  production  from  one 
another  by  gradual  change.  That  evidence  it  has  not  yet  af- 
forded. This  is  admitted  by  all,  even  by  those  who  believe 
that  the  transitions  were  gradual.  Geology  has  brought  to 
light  fewer  examples  of  gradual  transition  than  occur  among 
living  species.  The  wide  intervals  that  have  separated  related 
groups  are  diminished  from  time  to  time  by  the  discovery  of 
remains  of  intermediate  species.  It  has  been  thus  for  the 
interval  between  the  Elephant  and  Mastodon,  and  for  that  be- 
tween the  Horse  of  modern  time  and  the  Tapir-like  animals 
of  the  early  Tertiary  (page  204) ;  and  the  same  in  many  other 
cases.  And  yet  the  new  species  found  have  still  strong  specific 
differences,  arid  those  that  have  thus  far  been  discovered  between 
the  Horse  and  Tapir  are  of  distinct  genera ;  so  that  the  idea 
of  abruptness  between  species  is  not  yet  set  aside  by  geological 
evidence. 

But  geological  evidence  on  this  point  is,  as  has  been  often 
urged,  far  from  satisfactory.  The  record  is  unquestionably 
very  imperfect.  The  following  are  examples. 

It  is  certain  that  there  were  birds  in  the  Jurassic  period 
in  Europe,  for  one  with  its  feathers  has  been  found  fossil. 
But  thus  far  we  know  of  but  that  one  specimen  out  of  the 
many;  for  if  there  was  one  there  were  myriads. 


PROGRESS  IN  LIFE.  251 

There  is  the  same  evidence  that  there  were  Marsupial  Mam- 
mals during  the  Triassic  era  in  North  America,  and  therefore 
during  the  Jurassic  and  Cretaceous  eras  following;  and  yet 
only  two  jaw-bones  of  Triassic  Marsupials  have  been  found  in 
all  the  American  Mesozoic  rocks. 

There  was  abundant  life  in  the  oceans  of  the  long  Triassic 
and  Jurassic  eras;  but,  nevertheless,  not  a  fragment  of  any 
species  has  been  found  in  the  Triassic  or  Jurassic  rocks  on 
the  Atlantic  border  of  North  America;  and  the  Triassic  of 
the  Rocky  Mountain  region  is  as  destitute  of  marine  life.  The 
American  record  respecting  marine  species  of  the  Atlantic 
border  for  the  long  time  between  the  Carboniferous  and  Cre- 
taceous eras  is  utterly  a  blank. 

Again,  of  the  plants  of  the  great  forests  that  covered  the 
American  continent  in  the  Triassic  and  Jurassic  eras  less  than 
50  species  are  known;  and  yet  the  whole  of  the  dry  land  of 
the  continent  must  have  been  covered,  and  the  kinds  through 
all  that  time  must  have  been  very  numerous. 

These  are  examples  of  the  imperfection  in  the  record,  and 
they  naturally  weaken  much  the  force  of  geological  evidence. 
But  if  they  weaken  it,  they  do  not  authorize  the  conclusion 
that  the  transitions  were  always  gradual. 

There  are  some  gaps  of  great  width.  Of  the  species  con- 
necting Mollusks  or  other  Invertebrates  with  the  first  of 
Eishes,  geology  has  afforded  not  a  fact:  it  has  found  only 
great  Sharks,  Ganoids,  and  Placoderms  as  the  earliest  spe- 


252  GEOLOGICAL  HISTORY. 

cies.  With  regard  to  the  Palms,  which  first  appeared  in  the 
Cretaceous,  none  of  the  preceding  links  have  been  found;  and 
none  for  the  Elm,  Magnolia,  and  various  other  Angiosperms 
that  accompanied  the  first  Palms.  Bones  of  true  Mammals 
are  very  abundant  in  the  Tertiary  strata;  and  yet  in  the  Cre- 
taceous beds,  those  next  earlier,  there  are  numerous  remains 
of  great  Reptiles,  and  not  a  trace,  as  yet  observed,  of  the 
true  Mammals. 

8.  Origin  of  Man.  —  The  interval  between  the  Monkey  and 
Man  is  one  of  the  greatest.  The  capacity  of  the  brain  in  the 
lowest  of  men  is  68  cubic  inches,  while  that  in  the  highest 
Man- Ape  is  but  34.  Man  is  erect  in  posture,  and  has  this 
erectness  marked  in  the  form  and  position  of  all  his  bones, 
while  the  Man- Ape  has  his  inclined  posture  forced  on  him 
by  every  bone  of  his  skeleton.  The  highest  of  Man-Apes,  the 
Orang-utan,  cannot  walk  without  holding  on  by  his  fore- 
limbs  ;  and,  instead  of  having  a  double  curvature  in  his  back 
like  Man,  which  well-balanced  erectness  requires,  he  has  but 
one.  The  connecting  links  between  Man  and  any  Man- Ape 
of  past  geological  time  have  not  been  found,  although  earnestly 
looked  for.  No  specimen  of  the  Stone  age  that  has  yet  been 
discovered  is  inferior,  as  already  remarked,  to  the  lowest  of 
existing  men;  and  none  is  intermediate  in  essential  characters 
between  Man  and  the  Man-Ape.  Until  the  long  interval  is 
bridged  over  by  the  discovery  of  intermediate  species,  it  is 
certainly  unsafe  to  declare  that  such  a  line  of  intermediate 
species  ever  existed,  and  as  uuphilosophical  as  it  is  unsafe. 


PROGRESS  IN  LIFE.  253 

If,  then,  the  present  teaching  of  geology  as  to  the  origin 
of  species  is  for  the  most  part  indecisive,  it  still  strongly 
confirms  the  belief  that  Man  is  not  of  Nature's  making. 
Independently  of  such  evidence,  Man's  high  reason,  his  un- 
satisfied aspirations,  his  free  will,  all  afford  the  fullest  assur- 
ance that  he  owes  his  existence  to  the  special  act  of  the 
Infinite  Being  whose  image  he  bears. 

9.  Man  the  highest  species.  —  It  is  sometimes  queried  whether 
the  future  may  not  have  its  various  new  species  of  life,  and, 
among  them,  some  higher  than  existing  Man;  whether  the 
age  now  passing  is  not  to  be  followed,  as  was  true  of  the 
Carboniferous,  or  the  Reptilian,  by  another  still  more  glorious 
in  its  living  species;  whether,  if  one  of  the  great  Dinosaurs 
of  the  Mesozoic  age  could  have  thought  about  his  own  and 
other  times,  he  would  not  have  imagined  his  age  the  last  and 
the  best  possible,  and  whether  Man  is  not  playing  as  foolish 
a  part  in  styling  himself  the  "  lord  of  creation." 

Against  the  introduction  of  new  species  in  coming  time 
science  has  little  to  urge.  But  there  is  strong  reason  for 
holding  that,  whatever  the  changes  in  the  lower  tribes,  exist- 
ing Man  will  always  remain  the  highest  in  the  series. 

(1.)  Science  has  made  known  that  the  highest  of  species 
next  to  Man,  that  is,  the  brute  Mammals,  have  already  passed 
their  maximum  (page  225) ;  hence,  the  rest  of  time  remains 
for  the  culmination  of  the  only  higher  type,  that  of  Man. 
And,  as  this  type  includes  now  but  one  species,  we  have  rea- 
son for  expecting  no  new  species  in  the  future. 


254  GEOLOGICAL  HISTORY. 

(2.)  From  geological  history  we  learn  also  that  the  type  of 
Yertebrates  commenced  in  kinds  that  were  horizontal  in  atti- 
tude,—  the  Fishes;  and  that  from  the  horizontal  there  was, 
in  the  B/eptiles  and  Mammals,  a  raising  of  the  head  above 
the  line  of  the  body,  up  to  the  Ape,  in  which  the  attitude  is 
nearly  vertical;  and,  finally,  to  perfect  vertically  in  Man,  a 
being  having  the  head  placed  directly  over  the  body  and  hind 
limbs.  Thus,  as  Agassiz  observed,  the  last  term  in  the  series 
has  been  reached;  there  can  be  nothing  beyond.  This  is  true 
as  to  the  general  type  of  structure;  but  it  leaves  it  an  open 
question  whether  there  may  not  be  other  species  of  Man,  or 
erect  beings,  of  still  higher  grade. 

(3.)  But  a  different  species  of  Man  higher  than  existing  Man 
is  not  a  possibility.  We  can  conceive  of  other  species  of  Man 
distinguished  by  having  some  of  the  external  features  of  the 
Man-Apes.  But  these  are  marks  of  inferiority,  and,  if  possi- 
ble in  a  type  of  so  high  grade,  could  belong  only  to  inferior 
species. 

The  increasing  erectness  and  breadth  of  forehead  in  Man, 
and  the  shortening  of  the  jaws,  giving  a  nearly  vertical  line 
to  the  front,  which  are  a  known  result  of  culture,  indicate 
the  course  which  upward  progress  must  take.  And  in  these 
points  and  some  others  closely  related,  the  limits  of  perfec- 
tion have  been  nearly  reached  by  some  among  the  present 
race.  Further  improvement  can  give  physically  only  larger 
capacity  to  the  brain  and  greater  beauty  of  form  to  the 


PROGRESS  IN  LIFE.  255 

whole  structure,  and  make  these  qualities  more  general.  No 
wide  divergence  from  existing  Man  can  be  conceived  of. 
When  all  possible  change  in  these  directions  has  been  accom- 
plished, Man  will  still  be  Man,  and  no  more  the  head  of  the 
system  of  life  than  he  is  at  present. 

(4.)  Beyond  all  this  we  may  say,  that  since  no  Dinosaur,  and 
no  other  species  but  Man,  has  ever  been  capable  of  reviewing 
the  past  or  contemplating  the  future;  and  since  Man  not  only 
has  all  time  and  all  Nature  within  the  range  of  his  thought 
and  study,  but  can  even  yoke  Nature  for  service,  and  in  fact 
has  her  already  at  work  for  him  in  numberless  ways,  —  the 
system  with  such  a  head  must  be  complete. 

Nature,  through  Man,  has  attained  to  the  possession  of  a 
living  soul  capable  of  putting  her  once  wasted  energies  into 
strong  and  combined  movement  for  social,  intellectual,  and 
moral  purposes,  and  this  is  the  consummation  that  the  past 
has  ever  had  in  prospect. 

The  Man  of  the  future  is  Man  triumphant  over  dying 
Nature,  exulting  in  the  freedom  and  privileges  of  spiritual 
life. 


INDEX 


NOTE.  —The  pronunciation  of  some  of  the  scientific  words  is  indicated  by  an  accent. 


ACONCA'GUA,  65. 
Ac'rogens,  103. 

Carboniferous,  156. 
Adirondacks,  107- 
Agate,  5. 

Ages  in  Geology,  99. 
Alabama  Eocene,  201. 
Albite,  2. 

Algae.     See  SEA-WEEDS. 
Alleghany  Mountains,  making  of,  168. 
Alluvial  deposits,  49. 
Alps,  glaciers  in,  58. 

elevation  of,  20?. 
Amethyst,  11. 
Ammonites,  182. 
Amphibians,  163, 186. 
Amygdaloid,  18. 
An'giosperms,  Cretaceous,  181. 

Tertiary,  200. 
Anisopus,  tracks  of,  18?. 
Anthracite,  154. 

origin  of,  171. 
Anticli'nal,  85. 
Apennines,  207- 
Appalachians,  making  of,  168. 
Appalachian  region,  135, 136, 167. 

folded  rocks  of,  85, 169. 

thickness  of  formations  of,  167. 
Archse'an  time,  106. 

North  America,  108. 
Arequi'pa,  65. 
Argillaceous  sandstone,  15. 
Ar'gyllite,  15. 
Articulates,  100. 
As'aphus  gigas,  126. 
As'terophyllites,  140. 
Astrsea,  28. 

Atmosphere,  agency  of,  44. 
Augite,  8. 


Au'rochs,  232. 
Aymestry  limestone,  131. 
Azoic.    See  ARCHAEAN. 

BAI^  beds,  117- 
Basalt,  18. 

Basaltic  columns,  22. 
Beach-formations,  51. 
Bear,  cave,  225. 
Belem'nites,  184. 
Bilin,  infusorial  bed  of,  36. 
Birds,  101, 164. 

Jurassic  and  Cretaceous,  190. 

Tertiary,  203. 
Bituminous  coal,  154. 
Black  lead,  9. 
Blue  Ridge,  107. 
Bog  Iron-ore,  12. 
Bowlders,  211,  214. 
Bowlder-clay,  218. 
Brachiopods,  Silurian,  121, 133. 

Devonian,  142. 

Carboniferous,  152. 
Brains,  growth  in,  247. 
Brines  of  Salina,  130. 
Bryozo'ans,  125. 

CALAMI'TES,  140, 158. 
Calcareous  rocks,  14,  27. 
Calcite,  9. 

Calyme'ne  Blumenbachii,  126. 
Cambrian.    See  PRIMORDIAL. 
Camel,  Tertiary,  206. 
Cannel  coal,  154. 
Canon.    See  COLORADO. 
Carbon,  8. 

Carbonate  of  lime,  9. 
Carbonic  acid,  9. 
Carboniferous  age,  149. 


258 


INDEX. 


Carboniferous  age,  changes  during,  164. 

Car'ni-vores,  304. 

Carpathians,  207. 

Catskill  period,  138. 

Cave  animals  of  Quaternary,  225. 

Cenozoic  time,  194. 

Centipedes,  162. 

Cephalization,  progress  in,  249. 

Cephalopods,  123. 

of  Mcsozoic,  182. 
Cestracionts,  145. 
Chain-coral,  132. 
Chalcopy'rite,  13. 
Chalk,  179. 

Chainplain  period,  218. 
Chemung  beds,  138. 
Cincinnati  uplift,  135, 165. 
Circumdenudation,  81. 
Clay-slate,  15. 
Climate,  progress  in,  238. 

Mesozoic,  209. 

Quaternary,  215,  218,  230. 

Tertiary,  209. 
Coal,  kinds  of,  154. 

formation  of,  155. 

of  Rocky  Mountain  region,  197- 

sulphur  in,  155. 
Coal-areas,  American,  152. 

-areas  of  Britain,  153. 

-beds,  characters  of,  153. 

-beds,  formation  of,  165. 

-beds  of  Triassic,  175. 

-beds,  flexures  in,  169. 

-measures,  151. 

-period,  151. 

-plants,  age  of,  103, 149. 
Coccoliths,  34,  40. 
Coccos'teus,  147. 
Cockroaches,  161. 

Colora'do,  canon  of,  20,  77,  78,  237. 
Columna'ria,  119. 
Conformable  strata,  88. 
Conglomerate,  14. 
Conifers,  Devonian,  142. 

Carboniferous,  156, 160. 

Mesozoic,  180. 
Connecticut  River  sandstone  and  footprints,  175. 

terraces,  222. 

trap  rocks,  194. 
Continents  denned  in  Archaean  time,  108. 

origin  of,  94. 
Contraction  a  cause  of  change  of  level,  89. 


Copper  ore,  13. 
00^13,27-30. 

Silurian,  109, 119, 132. 

Devonian,  142. 

Carboniferous,  151. 
Corallines,  34. 
Corniferous  limestone,  137. 
Cotopaxi,  65. 
Craters,  65. 

Crepid'ula  costata,  201. 
Cretaceous  period,  175. 

America,  map  of,  177. 

Great  Britain,  map  of,  178. 
Crinoidal  limestone,  34, 150. 
Cri'noids,  30,  34, 100. 

Silurian,  119, 132. 

Subcarboniferous,  150. 
Crocodiles,  189. 
Crusta'ceans,  100. 
Cryp'togams,  103. 
Crystalline  rocks,  15-18,  26. 
Culmination  of  types,  102. 
Currents,  oceanic,  50. 
Cy'athophyl'loid  corals,  142. 
Cycads,  174, 181. 

DAWKINS,  W.  B.,  on  human  relics,  234. 

Decay  of  rocks,  42. 

Deer,  Irish,  226. 

Delta  of  Mississippi,  49. 

Den'udation,  48,  81,  86. 

Detri'tus,  25. 

Development,  system  of,  243. 

Devonian  age,  137- 

hornstone,  138. 
Diamond,  8. 
Di'atoms,  5,  35. 
Dikes,  65. 
Dinoceras,  204. 
Dinosaurs,  187. 
Dip,  83. 

Dodo,  extinction  of,  237. 
Dol'eryte.    See  TEAP. 
Dol'omite,  10. 
Drift,  211,  213 

sands,  45. 

scratches,  212. 
Dromatherium,  191. 
Dunes,  45. 

EARTH,  first  condition  of,  106,  238. 
progress  in  features,  238. 


INDEX. 


259 


Earth,  progress  in  life,  240. 

Earthquakes,  64,  88. 

Elephant,  Quaternary,  226,  232. 

Elevations,  causes  of,  80. 

Emery,  6. 

Ena'liosaurs,  or  Sea-saurians,  164,  188. 

England,  geological  map  of,  114, 178. 

E'ocene,  194. 

Eosau  rus,  104. 

Eozoon,  112. 

Equise'ta,  139, 156. 

Erosion,  48,  81. 

Evolution,  243. 

Expansion  of  rocks,  effects  of,  63. 

FAULTS,  75,  87, 176. 
Fa'vosi'tes,  143. 
Feldspar,  6. 
Ferns,  Devonian,  139. 

Carboniferous,  157, 158. 
Fingal's  cave,  208. 
Fishes,  101. 

Age  of,  137- 

Carboniferous,  161. 

Devonian,  144. 

Mesozoic,  185. 

Silurian,  133. 

Teliost,  186. 
Fish-spines,  144. 
Flags,  15, 139. 
Flexures,  84,  89. 
Flint,  4, 38, 180. 
Flint  arrow-heads,  230. 
Folded  rocks,  84,  89, 169. 
Footprints.    See  TKACKS. 
Foramin'ifers,  32. 

Fossils,  use  of,  in  determining  the  equivalency 
of  strata,  97- 

number  of  Paleozoic,  136. 
Fox,  Quaternary,  226. 
Fractures,  87, 176. 
Fragmental  rocks,  15. 
Fresh  waters,  action  of,  46. 
Fruits,  fossil,  160. 

GALE'NA,  13. 

Gan'oids,  Carboniferous,  161. 

Devonian,  144, 145. 

Triassic,  186. 
Garnet,  8. 
Gas'teropods,  122. 
Geysers,  69,  73. 


Giants'  Causeway,  18,  208. 
Glacial  period,  211. 
Glacier  period  of  Switzerland,  58,  217. 
second,  of  Europe,  223,  235. 

scratches,  60,  221. 
Glaciers,  58,  213. 
Glyptodon,  229. 
Gneiss,  16. 
Gon'iatites,  183. 
Gran'ite,  15. 
Graph'ite.  9, 112. 
Gravel,  15. 

Greenland,  changes  of  level  in,  237- 
Green  Mountains,  making  of,  128, 135, 165. 

limestone  of,  128. 
Green  River  Basin,  197. 
Grit,  23. 

Ground  Pines,  131. 
Gym'nosperms,  142. 
Gypsiferous  formation,  Triassic,  176. 

HALYSI'TES,  132. 

Hamilton  group,  138. 

Hawaii,  volcanoes  of,  66,  68. 

Heat,  63. 

Height  of  Mount  Shasta  and  other  volcanic 

peaks,  65. 

Helderbcrg  group,  130, 138. 
Hem'atite,  11, 12. 
Her'bi-vores,  203. 
Highlands,  107. 
Hippopotamus,  226. 
Holoptych'ius,  146. 
Hornblende,  7. 
Hornblende  rocks,  17, 109. 
Hornstone,  4,  38. 
Horse,  fossil,  204,  226. 
Hot  springs,  68. 
Human  skeletons,  fossil,  231. 
Hyaena,  cave,  225. 

ICE  of  lakes  and  rivers,  57. 

glacier,  58,  211. 
Icebergs,  62. 

down  the  Mississippi  valley,  219. 
Ichthyosaurus,  188. 
Igneous  rocks,  63. 

Tertiary,  208. 

Triassic,  194. 
Iguan'odon,  188. 
Infusorial  earth,  36. 
Insects,  Devonian,  143. 


260 


INDEX. 


Insects,  Carboniferous,  162. 
Invertebrates,  102. 
Irish  Deer,  226. 
Iron  ores,  11,  12. 

Archaean,  109, 110. 
Iron  mountains  of  Missouri,  109. 

JOINTS  in  rocks,  88. 
Jorullo,  66. 
Jurassic  period,  175. 

KILAUE'A,  67- 
Kitchen-middens,  232. 

LABKADOKITE,  7- 

Lake  Champlain  in  the  Quaternary,  219. 

Lakes  of  Rocky  Mountain  region,  Tertiary,  196. 

Lamellibranchs,  122. 

Laminated  structure,  15. 

Lateral  pressure,  89. 

Lava,  19.      . 

Layer,  21. 

Lead  ore,  13. 

Lemur,  264. 

Lepidoden'drids,  141, 157. 

Lepte'na,  121. 

Level,  change  of,  in  Sweden  and  Greenland,  237- 

changes  of,  in  the  Quaternary,  215,  218. 

origin  of  changes  of,  89. 
Lias,  177. 
Life,  agency  of,  in  rock-making,  27- 

general  laws  of  progress  of,  240. 
Lignite,  197. 
Lignitic  beds,  197,  202. 
Limestone,  9,  10, 13 

formation  of,  27,  33. 
Lingulella,  120. 
Lingula  flags,  117, 120. 
Lion,  cave,  225. 
Lirioden'dron,  181. 
Lithostrotion  Canadense,  151. 
Llandeilo  flags,  117. 
Llandovery  beds,  117. 
Lower  He'lderbevg,  130. 
Ludlow  group,  131. 
Ly'copods,  131,  141,  156. 
Lynx,  Quaternary,  226. 

MADREPORA,  28. 

Magnesian  limestone,  11, 13, 116. 

Magnetite,  11. 

Mammals,  101. 

Age  of,  99,  194.     . 


Mammals,  first  of,  190. 
Tertiary,  203. 
Quaternary,  225. 
Man,  Age  of,  209. 
relics  of,  230. 

the  head  of  the  system  of  life,  237,  253. 
origin  of,  252. 
Map  of  England,  114,  178. 

of  North  America,  Archaean,  105. 
of  North  America,  Cretaceous,  177. 
of  North  America,  Tertiary,  195. 
Marble,  14. 

of  Green  Mountains,  128. 
Marsh,  0.  C.,  growth  of  brains,  247. 
Marsupials,  191,  203. 
Quaternary,  229. 
Mastodon,  Quaternary,  226. 
May-flies,  Devonian,  144. 
Medina  group,  130. 
Megaceros.    See  IRISH  DEER. 
Meg'alosaur,  188. 
Megatherium,  228. 
Mento'ne  skeleton,  233. 
Mes'ozoic  time,  174. 
Metamorphic  rocks,  26. 
Metamorphism,  71,  89. 
Mia'mia  Bronsoni,  144. 
Mica,  7. 

schist,  16. 
Microscopic  organisms,  32,  35. 
Millstone-grit,  152. 
Mineral  coal.     See  COAL. 
Miocene,  194. 

Mississippi  River,  delta  of,  49. 
detritus  of,  48. 

valley,  in  the  Glacial  and  Champlain  pe- 
riods, 219. 
Missouri  iron  ores,  109. 
Mollusks,  27, 100. 
Monkeys,  204. 
Monument  Park,  82. 
Moraine,  60. 
Mo'sasaur,  190. 
Mosses,  131. 

Mountains,  making  of,  80,  83,  89, 171. 
of  Paleozoic  origin,  128,  148,  167- 
made  during  the  Mesozoic,  193. 
made  during  the  Tertiary,  206. 
Mount  Holyoke,  194. 
Hood,  208. 
Loa,66. 
Mansfield,  glacial  scratches  on,  213, 


INDEX. 


261 


Mount  Shasta,  64,  208. 

Tom,  194. 
Mountains,  White,  scratches  on,  213. 

White,  alpine  plants  on,  224. 
Mud,  15. 
Mud-cracks,  55. 
Myr'iapods,  or  Centipedes,  162. 

NAUTILUS,  in  the  Silurian,  124 
Neanderthal  skull,  233. 
Ne'olith'ic  era,  232. 
Niag'ara  group,  129. 

River,  gorge  of,  238. 
Nova  Scotia  coal-measures,  166. 
Num'mulites,  32,  33, 198. 
Nummulitic  limestone,  198, 199. 
Nullipores,  34. 
Nuts,  fossil,  160. 

OCEAN,  effects  of,  50. 

life  in  depths  of,  40. 
Oceanic  basin,  origin  of,  94. 
Old  red  sandstone,  139. 
On'onda'ga  limestone.      See  UPPER  HELDER- 

BERG. 

Oolyte,  178, 179. 
Opal,  5,  73. 
Ore'odon,  204. 

Organic  remains,  rocks  made  of,  25. 
Oris'kany  sandstone,  131. 
Orthis,  121. 
Orthoceras,  124. 
Or'thoclase,  7- 
Ostrea  sellseformis,  201. 
Otozoum  Moodii,  187. 
Owl,  203. 
Ox,  first  of,  206. 
Oyster,  Tertiary,  201. 

PAL'^EASTER,  120. 
Paleolith'ic  era,  231. 
Paleozo'ic  time,  113. 
Palisades,  194. 
Palms,  Cretaceous,  181. 

Tertiary,  209. 
Paradox'ides,  126. 
Parrot,  203. 
Peat,  formation  of,  40. 
Pentac'rinus,  31. 
Pen'tremi'tes,  151. 
Permian  group,  156. 
Plac/oderms,  147. 


Plants,  Archaean,  112. 

Carboniferous,  156. 

Cretaceous,  181. 

Devonian,  139. 

lime-secreting,  34. 

Lower  Silurian,  117. 

Upper  Silurian,  131. 

Tertiary,  200. 

Triassic,  180. 

Platephem'era  antiqua,  144. 
Ple'siosaurs,  189. 
Pleurotoma'ria  lenticula'ris,  123 
Pliocene,  194. 

Plumba'go.    See  GRAPHITE. 
Polycystines,  37- 
Polyps,  28, 100. 

Polythala'mia.    See  FORAMINIFERS. 
Porphyry,  19. 
Portage  group,  138. 
Portland  (England)  dirt-bed,  1?9. 
Post-tertiary.    See  QUATERNARY. 
Potsdam  sandstone,  116. 
Primordial  period,  116. 
Productus,  152. 
Progress  of  life,  242. 
Pro'tozo'ans,  99,  112, 118. 
Pterichthys,  147- 
Pterodactyl,  191. 
Pterosaurs,  190. 
Pudding-stone,  14. 
Pyrenees,  207. 
Pyrite,  10. 
Pyroxene,  8. 

QUADRUPEDS.    See  MAMMAJLS. 
Quaternary  Age,  209,  224. 
Quartz,  3. 
Quicklime,  9. 

RA'DIATES,  30,  99. 
Rain-prints,  56. 
Ran'iceps  Lyellii,  163. 
Recent  period,  221. 
Reefs,  coral,  33. 
Reindeer  era,  224,  231. 
Reptiles,  101. 

Carboniferous,  161, 163, 164. 

Mesozoic,  186. 
Reptilian  age,  174. 
Rhine,  alluvial  deposits  of,  221. 
Rhinoceroses,  Tertiary,  203. 

Quaternary,  226. 


262 


INDEX. 


Rhi'zopods,  32,  33,  40,  99. 

Archaean,  112. 

Cretaceous,  179. 
Ripple-marks,  54. 
Rivers,  action  of,  47. 

of  Palezoic  origin,  56. 
River  terraces,  222. 
Roches  moutonuees,  61,  216. 
Rocks,  Archaean,  106. 

fragmental,  25. 

kinds  of,  3, 13. 

making  of,  23,  33,  35,  44. 

metamorphic,  26. 

of  Mississippi  valley,  136. 

stratified,  19,  21,  25. 

thickness  of  Lower  Silurian,  129. 

thickness  of  Paleozoic  in  North  America, 
167. 

unstratified,  21. 
Rocky  Mountains,  origin  of,  193,  206. 

Mountain  coal-area,  198. 
Rotalia,  32. 

ST.  LAWRENCE  River  in  the  Quaternary,  219, 

221. 
Saliferous  group  of  Britain  and  Europe,  177- 

rocks  of  New  York,  130. 
Sali'na  rocks,  130. 
Salix,  Cretaceous,  181. 
Salt  of  Salina  and  Canada,  130. 

of  Triassic,  177. 
Sand,  15. 

Sand-scratches,  46. 
Sandstone,  14, 15. 
Sapphire,  6. 

Sassafras  Cretaceum,  181. 
Schist,  schistose  rocks,  16. 
Scoria,  19. 

Scratches,  glacial,  60,  212. 
Sea-beaches,  elevated,  221. 
Sea-saurians,  164, 188. 
Sea-weeds,  or  Algae,  112, 117. 
Sediment  of  Mississippi  River,  48. 
Sela'chians,  144,  161. 
Shale,  14. 
Sharks,  Devonian.  144. 

Carboniferous,  161. 

Tertiary,  202. 

Upper  Silurian,  133. 
Shasta,  64. 

Shells,  rocks  made  of,  27,  33. 
Sid'erite,  12. 


SigiUa'ria,  Sigillarids,  141, 159. 
Silica,  or  Quartz,  3,  5. 
Silicates,  5. 
Siliceous  plants,  35. 

sponges,  39. 

Polycistines,  37. 

waters  of  Geysers,  68. 
Silurian  age,  113. 

Lower,  115. 

Upper,  129. 
Skeletons  of  man,  231. 
Slate,  15. 

Sloths,  gigantic,  of  Quaternary,  227. 
Sol'fata'ras,  70. 
Solidification,  70. 
Spathic  iron  ore,  12. 

Species,  exterminations  of,  127, 173,  240. 
Sphagnous  mosses,  40. 
Sphenopteris  Gravenhorstii,  158. 
Spicules  of  Sponges,  37. 
Spiders,  100, 162. 
Spirifer,  152. 
Sponges,  37,  39,  79. 
Squid,  185. 
Stalactites,  24. 
Stalagmite,  24. 

containing  bones  of  cave  animals,  225,  233. 
Stone  age,  231. 
Strata,  definition  of,  21. 
Stratification,  19. 
Strike,  83. 

Subcarboniferous  period,  150. 
Subsidence  during  the  Champlain  period,  218, 

220. 

Sweden,  modern  change  of  level  in,  237. 
Sy'enyte,  17. 
Synclinal,  85. 
System  of  life,  242. 

TAILS  of  fishes,  145. 

Tapir,  203. 

Teliost  fishes,  186. 

Terrace  period.    See  RECENT  PEKIOD. 

Terraces  along  rivers,  221. 

Tertiary  age,  194. 

Time,  length  of  geological,  237,  239. 

Trach'yte,  19. 

Tracks  of  reptiles,  187. 

Transitions  between  species,  237. 

Trap,  18. 

of  Connecticut  valley,  etc.,  193. 

columnar,  22. 


INDEX. 


263 


Trav'ertine,  24. 
Tree-ferns,  157. 
Trenton  limestone,  117. 
Triassic  period,  17*. 
Tri'lobites,  125, 133, 142,  160. 
Tufa,  19. 

calcareous,  24. 

UNCONFORMABLE  strata,  88. 
Unstratified  rocks,  21. 
Uplifts,  89. 

Upper  Helderberg,  138. 
Upper  Silurian,  129. 

VALLEYS,  formation  of,  73. 
Veins,  formation  of,  73. 
Vertebrates,  110. 
Tertiary,  202. 
Vesuvius,  67. 
Volcanic  rocks,  18. 
Volcanoes,  64. 


WATER,  action  of  fresh,  46. 

action  of  oceanic,  50. 

freezing  and  frozen,  57. 
Waves,  action  of,  51. 
Weal'den,  179. 
Wenlock  limestone,  130. 
Whales,  first  of,  210. 
Willow,  Cretaceous,  181. 
Wind-drift  structure,  45. 
Wind  River  Mountains,  107. 
Winds,  effects  of,  44. 
White  Mountains,  glacial  scratches  on,  213. 

alpine  plants  on,  224. 
Wolf,  Quaternary,  226. 
Worms,  100. 

XIPHODON,  204. 
YELLOWSTONE  Park,  70. 
ZEACRINUS  elegans,  151. 


THE    END. 


University  Press,  Cambridge:  Electrotyped  and  Printed  by  Welch,  Bigelow,  &  Co. 


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